flood at log with, but it is not significant, this log message was present even on 18.06.4 version :
Mon Feb 10 08:00:11 2020 daemon.notice hostapd: ACS: Survey is missing noise floor
Mon Feb 10 08:00:11 2020 daemon.notice hostapd: ACS: Survey is missing noise floor
Mon Feb 10 08:00:11 2020 daemon.notice hostapd: ACS: Survey is missing noise floor
after upgrade to 19.07.1 wifi 5g get down randomly, so need to restart it manually. No important logs exists exclude mentioned flood during wifi restart on cron.
UPD: Associated Stations stopped showing 5g connections, but it is actually connected and works.
Do I need to do factory reset ? Because I kept settings during flash.