I applied the workaround script provided by @Catfriend1 in https://forum.openwrt.org/t/archer-c7-2-4-ghz-wireless-dies-in-24-48-hours/44163/211?u=nkef
that triggers "iw dev wlan0 scan trigger freq 2447 flush" when event 60 occurs.
https://github.com/Catfriend1/openwrt-presence/blob/master/scripts/ath9k-watchdog/ath9k-watchdog.sh