Did you find any resolution with this? I just had an end user open a ticket today about the same reason.
It s a Google Pixel 2 XL, was working fine until recently and now it just keeps connecting then disconnecting every 5-10 seconds
The errors in the log are "previous authentication expired" and then "client not authenticated" sometimes it will show Deauthentication information but most of the time its just 802.11 disassociation.
I am leaning toward it being a device issue, but it could also be something else, the Access Point he is connected to changed Channels frequently, but no where near as much as his phone is doing this.
It was on an SSID with a PSK, and even when the device is Whitelisted, it will not stay connected