It appears to be the session that is cleared, so it disrupts everything that device is currently doing for several seconds until the sessions are recreated.
I can see these logs under system events:
User: from cw_acd clean active IPv4 sessions,( filter:vd:0;source ip:172.30.100.10-172.30.100.10;)
And then these logs under WiFi Events:
Client 1c:1a:df:82:7b:74 de-authenticated.
Reason Previous authentication no longer valid
For all devices connected to WiFi and at exactly 00:00 every day.
FortiGate is a 61E running 7.0.3 and the FortiAP is a 221E also running 7.0.3, but it has happened on all versions of 7.0.x that I can remember.
Anyone have any suggestions how to diagnose or where to look next since I am stumped?