Device: Asus RT-N56U
Branch: openwrt-21.02, initial report commit 60fad8f (v21.02.0-rc3-74-g60fad8f82b)
Observation: when a wifi client disconnects that appears to see the AP with low signal strength, the whole AP goes down. Verified with airmon/tcpdump that AP beacons stop. Reboot of the router also observed when log_level set to 2 or lower.
Exactly same symptom from openwrt-21.02.0 as well as openwrt-21.02.1:
(1) One wifi client move far away (low signal) from AP
(2) ALL wifi clients connected to that AP disconnect and cannot find that AP (another AP from the same router has no problem, i.e. disconnect from 2.4GHz AP will not affect 5GHz AP)
(3) After around 1 minute, the disconnected AP re-appears and able to connect again