igmpproxy: broken in master

Maintainer: @ja-pa
Environment: cortex a9, mvebu, master (put here arch, model, OpenWrt version)

Description:
In OpenWRT 19.x i was able to watch IPTV without problems. Since (iirc) 21.xx i had some stutters and thought thats probably a problem by my ISP. Now i tested a master build and i can now watch only about 10 seconds before the stream fully stalls. As i use my own config, the same one for each build (i build the images myself), i guess this is not an openwrt problem but an igmpproxy one. in Openwrt 21.02.5 igmpproxy version 0.2.1-4 is used. I somehow can't believe its an upstream issue, but... no idea. IPTV is fully broken with master. I will see if i can find out when this started.
The only suspicious thing i found is a couple of those lines:
Fri Mar 31 23:38:21 2023 user.warn igmpproxy[32697]: MRT_DEL_MFC; Errno(2): No such file or directory

Start by reproducing the IPTV stream stall on an OpenWrt master build using the reported cortex A9/mvebu environment, then compare it with OpenWrt 21.02.5 and inspect the igmpproxy logs, including the MRT_DEL_MFC error. Done means identifying the regression and restoring stable streaming, or narrowing the issue to a confirmed upstream or configuration cause.