MT7621 (Netgear R6220) WiFi 5GHz problems (unable to connect)

After a few days I can not connect to the 5GHz WiFi (the problem occurs on 3 similar devices with firmware 21.xx.x).

Hardware:

Model	Netgear R6220
Architecture	MediaTek MT7621 ver:1 eco:3
Firmware Version	OpenWrt 21.02.0-rc4 r16256-2d5ee43dc6 / LuCI openwrt-21.02 branch git-21.188.55099-e52e1de
Kernel Version	5.4.137
Local Time	2021-08-16 18:12:52
Uptime	8d 1h 17m 24s

Kernel warning:

[344840.156837] ------------[ cut here ]------------
[344840.166626] WARNING: CPU: 0 PID: 903 at backports-5.10.42-1/net/mac80211/airtime.c:457 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.189800] Modules linked in: pppoe ppp_async iptable_nat xt_state xt_nat xt_conntrack xt_REDIRECT xt_MASQUERADE xt_FLOWOFFLOAD xt_CT pppox ppp_generic nf_nat nf_flow_table_hw nf_flow_table nf_conntrack mt76x2e mt76x2_common mt76x02_lib mt7603e mt76 mac80211 ipt_REJECT cfg80211 xt_time xt_tcpudp xt_multiport xt_mark xt_mac xt_limit xt_comment xt_TCPMSS xt_LOG slhc nf_reject_ipv4 nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 iptable_mangle iptable_filter ip_tables crc_ccitt compat ledtrig_usbport nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT x_tables nf_reject_ipv6 leds_gpio xhci_plat_hcd xhci_pci xhci_mtk xhci_hcd gpio_button_hotplug usbcore nls_base usb_common
[344840.312872] CPU: 0 PID: 903 Comm: mt76-tx phy1 Not tainted 5.4.137 #0
[344840.325867] Stack : 00000000 80850000 00000000 8007dec4 00000000 00000000 00000000 00000000
[344840.342675]         00000000 00000000 00000000 00000000 00000000 00000001 86ecbc30 7fa81504
[344840.359472]         86ecbcc8 00000000 00000000 00000000 00000038 805eaf64 00000018 35206465
[344840.376278]         00000000 00004305 00000000 746d203a 00000000 86ecbc10 00000000 86e57080
[344840.393075]         00000009 00000014 00000004 00000002 00000008 8035c19c 00000000 80820000
[344840.409872]         ...
[344840.414904] Call Trace:
[344840.414921] [<8007dec4>] 0x8007dec4
[344840.427090] [<805eaf64>] 0x805eaf64
[344840.434213] [<86e57080>] 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.446158] [<8035c19c>] 0x8035c19c
[344840.453275] [<8000b05c>] 0x8000b05c 
[344840.460381] [<8000b064>] 0x8000b064
[344840.467490] [<805d08a4>] 0x805d08a4
[344840.474599] [<8007a96c>] 0x8007a96c
[344840.481708] [<8002c140>] 0x8002c140
[344840.488830] [<86e57080>] 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.500782] [<8002c1e8>] 0x8002c1e8
[344840.507918] [<86e57080>] 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.519883] [<86e036f0>] 0x86e036f0 [mac80211@0d3ea537+0x7d9d0]
[344840.531851] [<86e57268>] 0x86e57268 [mac80211@0d3ea537+0x7d9d0]
[344840.543820] [<86e57348>] 0x86e57348 [mac80211@0d3ea537+0x7d9d0]
[344840.555782] [<8041dd74>] 0x8041dd74
[344840.562926] [<86ea2a24>] 0x86ea2a24 [mt76x02_lib@5e413cf1+0x9de0]
[344840.575243] [<86dd0530>] 0x86dd0530 [mt76@bec2abce+0x96c0]
[344840.586361] [<86dd0530>] 0x86dd0530 [mt76@bec2abce+0x96c0]
[344840.597457] [<86ea5004>] 0x86ea5004 [mt76x02_lib@5e413cf1+0x9de0]
[344840.609759] [<86dd0530>] 0x86dd0530 [mt76@bec2abce+0x96c0]
[344840.620863] [<86dd05d4>] 0x86dd05d4 [mt76@bec2abce+0x96c0]
[344840.631948] [<8004b484>] 0x8004b484
[344840.639054] [<805ec8fc>] 0x805ec8fc
[344840.646161] [<8004b994>] 0x8004b994
[344840.653267] [<8004b854>] 0x8004b854
[344840.660389] [<8004b854>] 0x8004b854
[344840.667508] [<8004b854>] 0x8004b854
[344840.674613] [<80006718>] 0x80006718
[344840.681719] 
[344840.686097] ---[ end trace e7dc2cbe445f2566 ]---

Kernel log:

[    0.000000] Linux version 5.4.137 (builder@buildhost) (gcc version 8.4.0 (OpenWrt GCC 8.4.0 r16256-2d5ee43dc6)) #0 SMP Sat Jul 31 17:21:01 2021
[    0.000000] SoC Type: MediaTek MT7621 ver:1 eco:3
[    0.000000] printk: bootconsole [early0] enabled
[    0.000000] CPU0 revision is: 0001992f (MIPS 1004Kc)
[    0.000000] MIPS: machine is Netgear R6220
[    0.000000] Initrd not found or empty - disabling initrd
[    0.000000] VPE topology {2} total 2
[    0.000000] Primary instruction cache 32kB, VIPT, 4-way, linesize 32 bytes.
[    0.000000] Primary data cache 32kB, 4-way, PIPT, no aliases, linesize 32 bytes
[    0.000000] MIPS secondary cache 256kB, 8-way, linesize 32 bytes.
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000000000000-0x0000000007ffffff]
[    0.000000]   HighMem  empty
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000000000-0x0000000007ffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000007ffffff]
[    0.000000] On node 0 totalpages: 32768
[    0.000000]   Normal zone: 288 pages used for memmap
[    0.000000]   Normal zone: 0 pages reserved
[    0.000000]   Normal zone: 32768 pages, LIFO batch:7
[    0.000000] percpu: Embedded 14 pages/cpu s26768 r8192 d22384 u57344
[    0.000000] pcpu-alloc: s26768 r8192 d22384 u57344 alloc=14*4096
[    0.000000] pcpu-alloc: [0] 0 [0] 1 
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 32480
[    0.000000] Kernel command line: console=ttyS0,57600 rootfstype=squashfs,jffs2
[    0.000000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
[    0.000000] Inode-cache hash table entries: 8192 (order: 3, 32768 bytes, linear)
[    0.000000] Writing ErrCtl register=0000c2e1
[    0.000000] Readback ErrCtl register=0000c2e1
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] Memory: 121076K/131072K available (6085K kernel code, 206K rwdata, 748K rodata, 1268K init, 238K bss, 9996K reserved, 0K cma-reserved, 0K highmem)
[    0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
[    0.000000] rcu: Hierarchical RCU implementation.
[    0.000000] rcu: 	RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=2.
[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[    0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=2
[    0.000000] NR_IRQS: 256
[    0.000000] random: get_random_bytes called from 0x806e3a3c with crng_init=0
[    0.000000] CPU Clock: 880MHz
[    0.000000] clocksource: GIC: mask: 0xffffffffffffffff max_cycles: 0xcaf478abb4, max_idle_ns: 440795247997 ns
[    0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 4343773742 ns
[    0.000009] sched_clock: 32 bits at 440MHz, resolution 2ns, wraps every 4880645118ns
[    0.015493] Calibrating delay loop... 583.68 BogoMIPS (lpj=1167360)
[    0.055798] pid_max: default: 32768 minimum: 301
[    0.065119] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.079517] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.097247] rcu: Hierarchical SRCU implementation.
[    0.107168] smp: Bringing up secondary CPUs ...
[    8.134241] Primary instruction cache 32kB, VIPT, 4-way, linesize 32 bytes.
[    8.134251] Primary data cache 32kB, 4-way, PIPT, no aliases, linesize 32 bytes
[    8.134262] MIPS secondary cache 256kB, 8-way, linesize 32 bytes.
[    8.134362] CPU1 revision is: 0001992f (MIPS 1004Kc)
[    0.144223] Synchronize counters for CPU 1: done.
[    0.203862] smp: Brought up 1 node, 2 CPUs
[    0.216148] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[    0.235416] futex hash table entries: 512 (order: 2, 16384 bytes, linear)
[    0.249033] pinctrl core: initialized pinctrl subsystem
[    0.260709] NET: Registered protocol family 16
[    0.277875] FPU Affinity set after 4688 emulations
[    0.298805] workqueue: max_active 576 requested for napi_workq is out of range, clamping between 1 and 512
[    0.319808] clocksource: Switched to clocksource GIC
[    0.331220] thermal_sys: Registered thermal governor 'step_wise'
[    0.331818] NET: Registered protocol family 2
[    0.352468] IP idents hash table entries: 2048 (order: 2, 16384 bytes, linear)
[    0.368052] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144 bytes, linear)
[    0.384577] TCP established hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.399784] TCP bind hash table entries: 1024 (order: 1, 8192 bytes, linear)
[    0.413754] TCP: Hash tables configured (established 1024 bind 1024)
[    0.426494] UDP hash table entries: 256 (order: 1, 8192 bytes, linear)
[    0.439378] UDP-Lite hash table entries: 256 (order: 1, 8192 bytes, linear)
[    0.453465] NET: Registered protocol family 1
[    0.462030] PCI: CLS 0 bytes, default 32
[    0.559715] 4 CPUs re-calibrate udelay(lpj = 1163264)
[    0.571170] workingset: timestamp_bits=14 max_order=15 bucket_order=1
[    0.597413] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[    0.608959] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[    0.630652] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 251)
[    0.647558] mt7621_gpio 1e000600.gpio: registering 32 gpios
[    0.658919] mt7621_gpio 1e000600.gpio: registering 32 gpios
[    0.670199] mt7621_gpio 1e000600.gpio: registering 32 gpios
[    0.682039] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[    0.698668] printk: console [ttyS0] disabled
[    0.707126] 1e000c00.uartlite: ttyS0 at MMIO 0x1e000c00 (irq = 15, base_baud = 3125000) is a 16550A
[    0.725052] printk: console [ttyS0] enabled
[    0.741599] printk: bootconsole [early0] disabled
[    0.762717] mt7621-nand 1e003000.nand: Using programmed access timing: 31c07388
[    0.777649] nand: device found, Manufacturer ID: 0xc2, Chip ID: 0xf1
[    0.790326] nand: Macronix MX30LF1G18AC
[    0.797971] nand: 128 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
[    0.813058] mt7621-nand 1e003000.nand: ECC strength adjusted to 4 bits
[    0.826098] mt7621-nand 1e003000.nand: Using programmed access timing: 21005134
[    0.840666] mt7621-nand 1e003000.nand: Using programmed access timing: 21005134
[    0.855241] Scanning device for bad blocks
[    2.162126] 6 fixed-partitions partitions found on MTD device mt7621-nand
[    2.175646] Creating 6 MTD partitions on "mt7621-nand":
[    2.186067] 0x000000000000-0x000000100000 : "u-boot"
[    2.197533] 0x000000100000-0x000000200000 : "SC PID"
[    2.208995] 0x000000200000-0x000000600000 : "kernel"
[    2.220460] 0x000000600000-0x000002200000 : "ubi"
[    2.231463] 0x000002e00000-0x000002f00000 : "factory"
[    2.243018] 0x000004200000-0x000007e00000 : "reserved"
[    2.256430] libphy: Fixed MDIO Bus: probed
[    2.290133] libphy: mdio: probed
[    2.296843] mt7530 mdio-bus:1f: MT7530 adapts as multi-chip module
[    2.313118] mtk_soc_eth 1e100000.ethernet eth0: mediatek frame engine at 0xbe100000, irq 17
[    2.332020] mt7621-pci 1e140000.pcie: Parsing DT failed
[    2.345582] NET: Registered protocol family 10
[    2.356022] Segment Routing with IPv6
[    2.363453] NET: Registered protocol family 17
[    2.372381] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[    2.398467] 8021q: 802.1Q VLAN Support v1.8
[    2.409530] mt7530 mdio-bus:1f: MT7530 adapts as multi-chip module
[    2.432074] libphy: dsa slave smi: probed
[    2.440543] mt7530 mdio-bus:1f lan4 (uninitialized): PHY [dsa-0.0:00] driver [Generic PHY]
[    2.458606] mt7530 mdio-bus:1f lan3 (uninitialized): PHY [dsa-0.0:01] driver [Generic PHY]
[    2.476677] mt7530 mdio-bus:1f lan2 (uninitialized): PHY [dsa-0.0:02] driver [Generic PHY]
[    2.494709] mt7530 mdio-bus:1f lan1 (uninitialized): PHY [dsa-0.0:03] driver [Generic PHY]
[    2.512825] mt7530 mdio-bus:1f wan (uninitialized): PHY [dsa-0.0:04] driver [Generic PHY]
[    2.530764] mt7530 mdio-bus:1f: configuring for fixed/rgmii link mode
[    2.548436] DSA: tree 0 setup
[    2.554763] rt2880-pinmux pinctrl: pcie is already enabled
[    2.565848] mt7621-pci-phy 1e149000.pcie-phy: PHY for 0xbe149000 (dual port = 1)
[    2.580793] mt7621-pci-phy 1e14a000.pcie-phy: PHY for 0xbe14a000 (dual port = 0)
[    2.695340] mt7621-pci-phy 1e149000.pcie-phy: Xtal is 40MHz
[    2.706459] mt7621-pci-phy 1e14a000.pcie-phy: Xtal is 40MHz
[    2.817300] mt7621-pci 1e140000.pcie: pcie1 no card, disable it (RST & CLK)
[    2.831171] mt7621-pci 1e140000.pcie: PCIE0 enabled
[    2.840892] mt7621-pci 1e140000.pcie: PCIE2 enabled
[    2.850615] mt7621-pci 1e140000.pcie: PCI coherence region base: 0x60000000, mask/settings: 0xf0000002
[    2.869345] mt7621-pci 1e140000.pcie: PCI host bridge to bus 0000:00
[    2.882031] pci_bus 0000:00: root bus resource [io  0x1e160000-0x1e16ffff]
[    2.895735] pci_bus 0000:00: root bus resource [mem 0x60000000-0x6fffffff]
[    2.909434] pci_bus 0000:00: root bus resource [bus 00-ff]
[    2.920414] pci 0000:00:00.0: [0e8d:0801] type 01 class 0x060400
[    2.932418] pci 0000:00:00.0: reg 0x10: [mem 0x00000000-0x7fffffff]
[    2.944913] pci 0000:00:00.0: reg 0x14: [mem 0x60400000-0x6040ffff]
[    2.957473] pci 0000:00:00.0: supports D1
[    2.965463] pci 0000:00:00.0: PME# supported from D0 D1 D3hot
[    2.977328] pci 0000:00:01.0: [0e8d:0801] type 01 class 0x060400
[    2.989345] pci 0000:00:01.0: reg 0x10: [mem 0x00000000-0x7fffffff]
[    3.001841] pci 0000:00:01.0: reg 0x14: [mem 0x60410000-0x6041ffff]
[    3.014391] pci 0000:00:01.0: supports D1
[    3.022386] pci 0000:00:01.0: PME# supported from D0 D1 D3hot
[    3.035505] pci 0000:01:00.0: [14c3:7662] type 00 class 0x028000
[    3.047551] pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x000fffff 64bit]
[    3.061120] pci 0000:01:00.0: reg 0x30: [mem 0x00000000-0x0000ffff pref]
[    3.074573] pci 0000:01:00.0: PME# supported from D0 D3hot D3cold
[    3.088240] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
[    3.098662] pci 0000:00:00.0:   bridge window [io  0x0000-0x0fff]
[    3.110805] pci 0000:00:00.0:   bridge window [mem 0x60000000-0x600fffff]
[    3.124343] pci 0000:00:00.0:   bridge window [mem 0x60100000-0x601fffff pref]
[    3.138742] pci_bus 0000:01: busn_res: [bus 01-ff] end is updated to 01
[    3.152147] pci 0000:02:00.0: [14c3:7603] type 00 class 0x028000
[    3.164175] pci 0000:02:00.0: reg 0x10: [mem 0x00000000-0x000fffff]
[    3.176801] pci 0000:02:00.0: PME# supported from D0 D3hot D3cold
[    3.190419] pci 0000:00:01.0: PCI bridge to [bus 02-ff]
[    3.200856] pci 0000:00:01.0:   bridge window [io  0x0000-0x0fff]
[    3.212999] pci 0000:00:01.0:   bridge window [mem 0x60200000-0x602fffff]
[    3.226533] pci 0000:00:01.0:   bridge window [mem 0x60300000-0x603fffff pref]
[    3.240931] pci_bus 0000:02: busn_res: [bus 02-ff] end is updated to 02
[    3.254168] pci 0000:00:00.0: BAR 0: no space for [mem size 0x80000000]
[    3.267348] pci 0000:00:00.0: BAR 0: failed to assign [mem size 0x80000000]
[    3.281226] pci 0000:00:01.0: BAR 0: no space for [mem size 0x80000000]
[    3.294405] pci 0000:00:01.0: BAR 0: failed to assign [mem size 0x80000000]
[    3.308283] pci 0000:00:00.0: BAR 8: assigned [mem 0x60000000-0x600fffff]
[    3.321813] pci 0000:00:00.0: BAR 9: assigned [mem 0x60100000-0x601fffff pref]
[    3.336216] pci 0000:00:01.0: BAR 8: assigned [mem 0x60200000-0x602fffff]
[    3.349746] pci 0000:00:01.0: BAR 9: assigned [mem 0x60300000-0x603fffff pref]
[    3.364143] pci 0000:00:00.0: BAR 1: assigned [mem 0x60400000-0x6040ffff]
[    3.377677] pci 0000:00:01.0: BAR 1: assigned [mem 0x60410000-0x6041ffff]
[    3.391207] pci 0000:00:00.0: BAR 7: assigned [io  0x1e160000-0x1e160fff]
[    3.404739] pci 0000:00:01.0: BAR 7: assigned [io  0x1e161000-0x1e161fff]
[    3.418278] pci 0000:01:00.0: BAR 0: assigned [mem 0x60000000-0x600fffff 64bit]
[    3.432859] pci 0000:01:00.0: BAR 6: assigned [mem 0x60100000-0x6010ffff pref]
[    3.447256] pci 0000:00:00.0: PCI bridge to [bus 01]
[    3.457154] pci 0000:00:00.0:   bridge window [io  0x1e160000-0x1e160fff]
[    3.470681] pci 0000:00:00.0:   bridge window [mem 0x60000000-0x600fffff]
[    3.484212] pci 0000:00:00.0:   bridge window [mem 0x60100000-0x601fffff pref]
[    3.498610] pci 0000:02:00.0: BAR 0: assigned [mem 0x60200000-0x602fffff]
[    3.512143] pci 0000:00:01.0: PCI bridge to [bus 02]
[    3.522036] pci 0000:00:01.0:   bridge window [io  0x1e161000-0x1e161fff]
[    3.535562] pci 0000:00:01.0:   bridge window [mem 0x60200000-0x602fffff]
[    3.549098] pci 0000:00:01.0:   bridge window [mem 0x60300000-0x603fffff pref]
[    3.564115] mt7530 mdio-bus:1f: Link is Up - 1Gbps/Full - flow control off
[    3.577856] random: fast init done
[    3.579079] UBI: auto-attach mtd3
[    3.591285] ubi0: attaching mtd3
[    3.882344] ubi0: scanning is finished
[    3.906265] ubi0: attached mtd3 (name "ubi", size 28 MiB)
[    3.917092] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
[    3.930834] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[    3.944360] ubi0: VID header offset: 2048 (aligned 2048), data offset: 4096
[    3.958232] ubi0: good PEBs: 224, bad PEBs: 0, corrupted PEBs: 0
[    3.970206] ubi0: user volume: 2, internal volumes: 1, max. volumes count: 128
[    3.984599] ubi0: max/mean erase counter: 5/3, WL threshold: 4096, image sequence number: 1514313493
[    4.002792] ubi0: available PEBs: 0, total reserved PEBs: 224, PEBs reserved for bad PEB handling: 20
[    4.021191] ubi0: background thread "ubi_bgt0d" started, PID 465
[    4.023478] block ubiblock0_0: created from ubi0:0(rootfs)
[    4.044151] ubiblock: device ubiblock0_0 (rootfs) set to be root filesystem
[    4.058035] hctosys: unable to open rtc device (rtc0)
[    4.075225] VFS: Mounted root (squashfs filesystem) readonly on device 254:0.
[    4.093786] Freeing unused kernel memory: 1268K
[    4.102864] This architecture does not have kernel memory protection.
[    4.115708] Run /sbin/init as init process
[    4.582203] init: Console is alive
[    4.589248] init: - watchdog -
[    5.368216] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[    5.470023] usbcore: registered new interface driver usbfs
[    5.481112] usbcore: registered new interface driver hub
[    5.491843] usbcore: registered new device driver usb
[    5.512084] xhci-mtk 1e1c0000.xhci: 1e1c0000.xhci supply vusb33 not found, using dummy regulator
[    5.529831] xhci-mtk 1e1c0000.xhci: xHCI Host Controller
[    5.540461] xhci-mtk 1e1c0000.xhci: new USB bus registered, assigned bus number 1
[    5.563891] xhci-mtk 1e1c0000.xhci: hcc params 0x01401198 hci version 0x96 quirks 0x0000000000290010
[    5.582184] xhci-mtk 1e1c0000.xhci: irq 16, io mem 0x1e1c0000
[    5.594919] hub 1-0:1.0: USB hub found
[    5.602566] hub 1-0:1.0: 2 ports detected
[    5.611224] xhci-mtk 1e1c0000.xhci: xHCI Host Controller
[    5.621923] xhci-mtk 1e1c0000.xhci: new USB bus registered, assigned bus number 2
[    5.636864] xhci-mtk 1e1c0000.xhci: Host supports USB 3.0 SuperSpeed
[    5.649747] usb usb2: We don't know the algorithms for LPM for this host, disabling LPM.
[    5.666761] hub 2-0:1.0: USB hub found
[    5.674352] hub 2-0:1.0: 1 port detected
[    5.688140] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[    5.716105] init: - preinit -
[    6.481763] mtk_soc_eth 1e100000.ethernet eth0: configuring for fixed/rgmii link mode
[    6.497841] mtk_soc_eth 1e100000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[    6.515232] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[    6.716338] random: jshn: uninitialized urandom read (4 bytes read)
[    6.836265] random: jshn: uninitialized urandom read (4 bytes read)
[    6.886696] random: jshn: uninitialized urandom read (4 bytes read)
[    7.133594] mt7530 mdio-bus:1f lan1: configuring for phy/gmii link mode
[    7.147201] 8021q: adding VLAN 0 to HW filter on device lan1
[   11.260364] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[   11.275380] IPv6: ADDRCONF(NETDEV_CHANGE): lan1: link becomes ready
[   11.414730] UBIFS (ubi0:1): Mounting in unauthenticated mode
[   11.426287] UBIFS (ubi0:1): background thread "ubifs_bgt0_1" started, PID 599
[   11.626571] UBIFS (ubi0:1): UBIFS: mounted UBI device 0, volume 1, name "rootfs_data"
[   11.642207] UBIFS (ubi0:1): LEB size: 126976 bytes (124 KiB), min./max. I/O unit sizes: 2048 bytes/2048 bytes
[   11.661966] UBIFS (ubi0:1): FS size: 20697088 bytes (19 MiB, 163 LEBs), journal size 1015809 bytes (0 MiB, 8 LEBs)
[   11.682635] UBIFS (ubi0:1): reserved for root: 977574 bytes (954 KiB)
[   11.695493] UBIFS (ubi0:1): media format: w5/r0 (latest is w5/r0), UUID 4BCBEF84-9C96-4565-8907-30ADDA2D96E1, small LPT model
[   11.720283] mount_root: overlay filesystem has not been fully initialized yet
[   11.735178] mount_root: switching to ubifs overlay
[   12.119208] urandom-seed: Seed file not found (/etc/urandom.seed)
[   12.246047] mt7530 mdio-bus:1f lan1: Link is Down
[   12.265645] procd: - early -
[   12.271596] procd: - watchdog -
[   12.891909] procd: - watchdog -
[   12.898584] procd: - ubus -
[   13.063846] procd: - init -
[   13.816410] kmodloader: loading kernel modules from /etc/modules.d/*
[   13.850508] Loading modules backported from Linux version v5.10.42-0-g65859eca4dff
[   13.865661] Backport generated by backports.git v5.10.42-1-0-gbee5c545
[   13.906843] xt_time: kernel timezone is -0000
[   13.941347] urngd: v1.0.2 started.
[   14.077741] mt7621-pci 1e140000.pcie: bus=2 slot=1 irq=21
[   14.088575] pci 0000:00:01.0: enabling device (0006 -> 0007)
[   14.099868] mt7603e 0000:02:00.0: enabling device (0000 -> 0002)
[   14.112136] mt7603e 0000:02:00.0: ASIC revision: 76030010
[   14.151322] random: crng init done
[   14.158133] random: 7 urandom warning(s) missed due to ratelimiting
[   14.741212] mt7603e 0000:02:00.0: Firmware Version: ap_pcie
[   14.752351] mt7603e 0000:02:00.0: Build Time: 20160107100755
[   14.787746] mt7603e 0000:02:00.0: firmware init done
[   14.969090] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
[   15.004100] mt7621-pci 1e140000.pcie: bus=1 slot=0 irq=19
[   15.014963] pci 0000:00:00.0: enabling device (0006 -> 0007)
[   15.026259] mt76x2e 0000:01:00.0: enabling device (0000 -> 0002)
[   15.038506] mt76x2e 0000:01:00.0: ASIC revision: 76120044
[   15.568598] mt76x2e 0000:01:00.0: ROM patch build: 20141115060606a
[   15.586860] mt76x2e 0000:01:00.0: Firmware Version: 0.0.00
[   15.597893] mt76x2e 0000:01:00.0: Build: 1
[   15.606148] mt76x2e 0000:01:00.0: Build Time: 201507311614____
[   15.631888] mt76x2e 0000:01:00.0: Firmware running!
[   15.643695] ieee80211 phy1: Selected rate control algorithm 'minstrel_ht'
[   15.675576] PPP generic driver version 2.4.2
[   15.687543] NET: Registered protocol family 24
[   15.716157] kmodloader: done loading kernel modules from /etc/modules.d/*
[   24.664339] mtk_soc_eth 1e100000.ethernet eth0: Link is Down
[   24.691442] mtk_soc_eth 1e100000.ethernet eth0: configuring for fixed/rgmii link mode
[   24.707663] mtk_soc_eth 1e100000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[   24.734341] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   24.751258] mt7530 mdio-bus:1f lan1: configuring for phy/gmii link mode
[   24.765287] 8021q: adding VLAN 0 to HW filter on device lan1
[   24.781322] br-lan: port 1(lan1) entered blocking state
[   24.792013] br-lan: port 1(lan1) entered disabled state
[   24.808616] device lan1 entered promiscuous mode
[   24.817894] device eth0 entered promiscuous mode
[   24.849907] mt7530 mdio-bus:1f lan2: configuring for phy/gmii link mode
[   24.863829] 8021q: adding VLAN 0 to HW filter on device lan2
[   24.892471] br-lan: port 2(lan2) entered blocking state
[   24.903002] br-lan: port 2(lan2) entered disabled state
[   24.916120] device lan2 entered promiscuous mode
[   24.937783] mt7530 mdio-bus:1f lan3: configuring for phy/gmii link mode
[   24.951880] 8021q: adding VLAN 0 to HW filter on device lan3
[   24.966864] br-lan: port 3(lan3) entered blocking state
[   24.977368] br-lan: port 3(lan3) entered disabled state
[   24.992739] device lan3 entered promiscuous mode
[   25.014641] mt7530 mdio-bus:1f lan4: configuring for phy/gmii link mode
[   25.029428] 8021q: adding VLAN 0 to HW filter on device lan4
[   25.046075] br-lan: port 4(lan4) entered blocking state
[   25.056640] br-lan: port 4(lan4) entered disabled state
[   25.070697] device lan4 entered promiscuous mode
[   25.106593] mt7530 mdio-bus:1f wan: configuring for phy/gmii link mode
[   25.122519] 8021q: adding VLAN 0 to HW filter on device wan
[   28.744741] br-lan: port 5(wlan1) entered blocking state
[   28.755394] br-lan: port 5(wlan1) entered disabled state
[   28.766645] device wlan1 entered promiscuous mode
[   28.848808] br-lan: port 6(wlan0) entered blocking state
[   28.859445] br-lan: port 6(wlan0) entered disabled state
[   28.870785] device wlan0 entered promiscuous mode
[   28.880450] br-lan: port 6(wlan0) entered blocking state
[   28.891183] br-lan: port 6(wlan0) entered forwarding state
[   28.902641] IPv6: ADDRCONF(NETDEV_CHANGE): br-lan: link becomes ready
[   29.058321] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[   29.199672] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0-1: link becomes ready
[   29.862034] IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
[   29.875234] br-lan: port 5(wlan1) entered blocking state
[   29.885967] br-lan: port 5(wlan1) entered forwarding state
[   29.916413] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[   29.932381] br-lan: port 1(lan1) entered blocking state
[   29.942877] br-lan: port 1(lan1) entered forwarding state
[   42.556288] mt7530 mdio-bus:1f wan: Link is Up - 1Gbps/Full - flow control rx/tx
[   42.571138] IPv6: ADDRCONF(NETDEV_CHANGE): wan: link becomes ready
[   43.580009] mt7530 mdio-bus:1f wan: Link is Down
[   49.724163] mt7530 mdio-bus:1f wan: Link is Up - 1Gbps/Full - flow control rx/tx
[   50.748017] mt7530 mdio-bus:1f wan: Link is Down
[   53.820173] mt7530 mdio-bus:1f wan: Link is Up - 1Gbps/Full - flow control rx/tx
[27223.057318] mt7530 mdio-bus:1f lan1: Link is Down
[27223.067250] br-lan: port 1(lan1) entered disabled state
[27225.105564] mt7530 mdio-bus:1f lan1: Link is Up - 100Mbps/Full - flow control rx/tx
[27225.120947] br-lan: port 1(lan1) entered blocking state
[27225.131452] br-lan: port 1(lan1) entered forwarding state
[60757.781941] mt7530 mdio-bus:1f lan1: Link is Down
[60757.791770] br-lan: port 1(lan1) entered disabled state
[60764.950136] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[60764.965162] br-lan: port 1(lan1) entered blocking state
[60764.975661] br-lan: port 1(lan1) entered forwarding state
[66275.054125] mt7530 mdio-bus:1f lan1: Link is Down
[66275.064045] br-lan: port 1(lan1) entered disabled state
[66278.126344] mt7530 mdio-bus:1f lan1: Link is Up - 100Mbps/Full - flow control rx/tx
[66278.141838] br-lan: port 1(lan1) entered blocking state
[66278.152297] br-lan: port 1(lan1) entered forwarding state
[66292.462031] mt7530 mdio-bus:1f lan1: Link is Down
[66292.471600] br-lan: port 1(lan1) entered disabled state
[171380.722706] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control off
[171380.737560] br-lan: port 1(lan1) entered blocking state
[171380.748231] br-lan: port 1(lan1) entered forwarding state
[171397.106370] mt7530 mdio-bus:1f lan1: Link is Down
[171397.117367] br-lan: port 1(lan1) entered disabled state
[171405.298533] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[171405.313717] br-lan: port 1(lan1) entered blocking state
[171405.324381] br-lan: port 1(lan1) entered forwarding state
[206294.088631] mt7530 mdio-bus:1f wan: Link is Down
[206384.200136] mt7530 mdio-bus:1f wan: Link is Up - 1Gbps/Full - flow control rx/tx
[206407.751808] mt7530 mdio-bus:1f wan: Link is Down
[206410.823965] mt7530 mdio-bus:1f wan: Link is Up - 1Gbps/Full - flow control rx/tx
[240934.373711] mt7530 mdio-bus:1f lan1: Link is Down
[240934.383683] br-lan: port 1(lan1) entered disabled state
[240937.445959] mt7530 mdio-bus:1f lan1: Link is Up - 100Mbps/Full - flow control rx/tx
[240937.461464] br-lan: port 1(lan1) entered blocking state
[240937.472142] br-lan: port 1(lan1) entered forwarding state
[256006.518328] mt7530 mdio-bus:1f lan1: Link is Down
[256006.528561] br-lan: port 1(lan1) entered disabled state
[256013.686521] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[256013.701709] br-lan: port 1(lan1) entered blocking state
[256013.712366] br-lan: port 1(lan1) entered forwarding state
[284926.107458] mt7530 mdio-bus:1f lan1: Link is Down
[284926.117646] br-lan: port 1(lan1) entered disabled state
[284929.179678] mt7530 mdio-bus:1f lan1: Link is Up - 100Mbps/Full - flow control rx/tx
[284929.195268] br-lan: port 1(lan1) entered blocking state
[284929.205941] br-lan: port 1(lan1) entered forwarding state
[314726.339789] mt7530 mdio-bus:1f lan1: Link is Down
[314726.349728] br-lan: port 1(lan1) entered disabled state
[314733.507989] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[314733.524449] br-lan: port 1(lan1) entered blocking state
[314733.535105] br-lan: port 1(lan1) entered forwarding state
[344840.156837] ------------[ cut here ]------------
[344840.166626] WARNING: CPU: 0 PID: 903 at backports-5.10.42-1/net/mac80211/airtime.c:457 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.189800] Modules linked in: pppoe ppp_async iptable_nat xt_state xt_nat xt_conntrack xt_REDIRECT xt_MASQUERADE xt_FLOWOFFLOAD xt_CT pppox ppp_generic nf_nat nf_flow_table_hw nf_flow_table nf_conntrack mt76x2e mt76x2_common mt76x02_lib mt7603e mt76 mac80211 ipt_REJECT cfg80211 xt_time xt_tcpudp xt_multiport xt_mark xt_mac xt_limit xt_comment xt_TCPMSS xt_LOG slhc nf_reject_ipv4 nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 iptable_mangle iptable_filter ip_tables crc_ccitt compat ledtrig_usbport nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT x_tables nf_reject_ipv6 leds_gpio xhci_plat_hcd xhci_pci xhci_mtk xhci_hcd gpio_button_hotplug usbcore nls_base usb_common
[344840.312872] CPU: 0 PID: 903 Comm: mt76-tx phy1 Not tainted 5.4.137 #0
[344840.325867] Stack : 00000000 80850000 00000000 8007dec4 00000000 00000000 00000000 00000000
[344840.342675]         00000000 00000000 00000000 00000000 00000000 00000001 86ecbc30 7fa81504
[344840.359472]         86ecbcc8 00000000 00000000 00000000 00000038 805eaf64 00000018 35206465
[344840.376278]         00000000 00004305 00000000 746d203a 00000000 86ecbc10 00000000 86e57080
[344840.393075]         00000009 00000014 00000004 00000002 00000008 8035c19c 00000000 80820000
[344840.409872]         ...
[344840.414904] Call Trace:
[344840.414921] [<8007dec4>] 0x8007dec4
[344840.427090] [<805eaf64>] 0x805eaf64
[344840.434213] [<86e57080>] 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.446158] [<8035c19c>] 0x8035c19c
[344840.453275] [<8000b05c>] 0x8000b05c
[344840.460381] [<8000b064>] 0x8000b064
[344840.467490] [<805d08a4>] 0x805d08a4
[344840.474599] [<8007a96c>] 0x8007a96c
[344840.481708] [<8002c140>] 0x8002c140
[344840.488830] [<86e57080>] 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.500782] [<8002c1e8>] 0x8002c1e8
[344840.507918] [<86e57080>] 0x86e57080 [mac80211@0d3ea537+0x7d9d0]
[344840.519883] [<86e036f0>] 0x86e036f0 [mac80211@0d3ea537+0x7d9d0]
[344840.531851] [<86e57268>] 0x86e57268 [mac80211@0d3ea537+0x7d9d0]
[344840.543820] [<86e57348>] 0x86e57348 [mac80211@0d3ea537+0x7d9d0]
[344840.555782] [<8041dd74>] 0x8041dd74
[344840.562926] [<86ea2a24>] 0x86ea2a24 [mt76x02_lib@5e413cf1+0x9de0]
[344840.575243] [<86dd0530>] 0x86dd0530 [mt76@bec2abce+0x96c0]
[344840.586361] [<86dd0530>] 0x86dd0530 [mt76@bec2abce+0x96c0]
[344840.597457] [<86ea5004>] 0x86ea5004 [mt76x02_lib@5e413cf1+0x9de0]
[344840.609759] [<86dd0530>] 0x86dd0530 [mt76@bec2abce+0x96c0]
[344840.620863] [<86dd05d4>] 0x86dd05d4 [mt76@bec2abce+0x96c0]
[344840.631948] [<8004b484>] 0x8004b484
[344840.639054] [<805ec8fc>] 0x805ec8fc
[344840.646161] [<8004b994>] 0x8004b994
[344840.653267] [<8004b854>] 0x8004b854
[344840.660389] [<8004b854>] 0x8004b854
[344840.667508] [<8004b854>] 0x8004b854
[344840.674613] [<80006718>] 0x80006718
[344840.681719] 
[344840.686097] ---[ end trace e7dc2cbe445f2566 ]---
[345640.667088] mt7530 mdio-bus:1f lan1: Link is Down
[345640.677221] br-lan: port 1(lan1) entered disabled state
[345643.739304] mt7530 mdio-bus:1f lan1: Link is Up - 100Mbps/Full - flow control rx/tx
[345643.755057] br-lan: port 1(lan1) entered blocking state
[345643.765773] br-lan: port 1(lan1) entered forwarding state
[345658.074961] mt7530 mdio-bus:1f lan1: Link is Down
[345658.084862] br-lan: port 1(lan1) entered disabled state
[345660.123178] mt7530 mdio-bus:1f lan1: Link is Up - 10Mbps/Full - flow control off
[345660.138730] br-lan: port 1(lan1) entered blocking state
[345660.149369] br-lan: port 1(lan1) entered forwarding state
[345677.530805] mt7530 mdio-bus:1f lan1: Link is Down
[345677.540688] br-lan: port 1(lan1) entered disabled state
[345687.770977] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[345687.786355] br-lan: port 1(lan1) entered blocking state
[345687.797055] br-lan: port 1(lan1) entered forwarding state
[349066.945430] mt7530 mdio-bus:1f lan1: Link is Down
[349066.955514] br-lan: port 1(lan1) entered disabled state
[349070.017664] mt7530 mdio-bus:1f lan1: Link is Up - 100Mbps/Full - flow control rx/tx
[349070.033214] br-lan: port 1(lan1) entered blocking state
[349070.043893] br-lan: port 1(lan1) entered forwarding state
[349085.377291] mt7530 mdio-bus:1f lan1: Link is Down
[349085.387157] br-lan: port 1(lan1) entered disabled state
[666069.429392] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control off
[666069.444231] br-lan: port 1(lan1) entered blocking state
[666069.454912] br-lan: port 1(lan1) entered forwarding state
[666086.837025] mt7530 mdio-bus:1f lan1: Link is Down
[666086.847337] br-lan: port 1(lan1) entered disabled state
[666096.053194] mt7530 mdio-bus:1f lan1: Link is Up - 1Gbps/Full - flow control rx/tx
[666096.068344] br-lan: port 1(lan1) entered blocking state
[666096.079011] br-lan: port 1(lan1) entered forwarding state
[692668.872871] device wlan1 left promiscuous mode

Start by reviewing the warning at backports-5.10.42-1/net/mac80211/airtime.c:457 and the mt76-tx call trace, then inspect the mt76x2e and mac80211 components shown in the logs. Reproduce the 5GHz connection failure on the Netgear R6220 with the reported firmware and verify that connections remain available after several days without the warning.