MT7986 - temporarily ping spikes and terrible WiFi performance - 5GHz, 160 MHz

Subject of the issue

Massive ping spikes and a bad WiFi performance (<50Mbit) are randomly occurring with the MT7986 chipset on both bands

Your environment

• MT6000 & TUF-AX6000
• Latest snapshot (r26128) & 23.05.3
• Public WiFi
• WED disabled, no software or hardware offloading, 5GHz, 160MHZ, client isolation on

Expected behavior

Stable and fast WiFi performance during the "good times":

Actual behavior

I'm having random horrible ping and WiFi performance problems with the MT7986 driver. This happens on the MT6000 and also the Asus TUF-AX6000 with all 5GHz and also sometimes 2.4 GHz clients, which are connected at the same time. The problems always occur every 10-30min lasting for around 5-10min until everything returns to normal. No errors in the logs. Via LAN cable the connection is always fast and stable.

This problem happened so far with every OpenWRT version which i tried. It does not happen with the stock firmware of both devices.

I have the feeling that its caused by specific WiFi clients, but it also seems to happen when AP-STA-POLL-OK is being sent.

Start with the MT7986 driver and reproduce the reported 5GHz 160 MHz behavior on the MT6000 or TUF-AX6000 using the listed OpenWrt versions and client-isolation settings. Compare the affected WiFi behavior with the stable LAN connection and observe whether the 10–30 minute degradation coincides with AP-STA-POLL-OK; done means identifying and correcting the cause of the recurring spikes and throughput loss.