I sometimes wonder if the wifi bugs are somehow related to the bugs with the mtk switch driver on mt7621, that wifi bugs out when the switchdriver has transmit timeouts and freezes.
For example here
He is somewhere on 19.7. firmware and says errors dissapear completely when using a vlan for every port.
A few posts above in this thread @eisengrau is running 19.07.3 stable, but also with vlans enabled.
However @dedors is writing that his 19.07.3 in ap mode is comepletly unstable (no vlans !?)
@morhimi are you using both 2.4ghz and 5ghz on snapshot and how many clients, just curious.