Client devices determine when to roam and troubleshooting client connectivity is a common need.
The log message included the key bits "hint=recv dissassociate (reason 8)", so the AP reported
receiving the dissassociate from the client. APs will follow these leaves with a clean-up sending
a dissassociate from the AP the client left (probably a few lines further in your logs).
Regarding 5G behavior specifically, if you live anywhere near a public airport or military base, you
can program your APs to avoid the middle UNII bands that have Radar/DFS associated with them.
APs seeing radar have to change channels and go silent, which can be disruptive for the brief
period.
Avoid this by setting your ZoneDirector's Configure/System, Country Code -> Channel Optimization
to Optimize for Compatibility choice. All 5G wireless clients should have no problem operating on
the channels available for Channelfly/Background Scanning selection, when you have this set.