I made the update to Android 9 yesterday after a long time on Android 7 with FP2.
Since then I randomly got stuck on the lockscreen.
It would display nothing (normally shows the time, battery level etc) and would not react to touchscreen actions. Buttons did work though, so I was able to turn on the (empty) screen, change the sound volume and to shut-down/restart. Weird thing, the touchscreen did work to select the “restart” option.
When restarting everything works fine. Until the next random time stuck on the lockscreen.
It’s really like I can’t unlock, and all informations are hidden.
I just tried to deactivate Google Screen lock service (which had admin rights to “determine the quality of the device’s screen lock”), I also deactived Google Pay which has also admin rights. I believe this is new to Android 9 because I had not seen those options before.
I’ll see if the issue still happens after that.
It looks like a bug anyway.
Maybe related but looks different: Fairphone 3 stuck at lockscreen