Found a possible fix that has worked on the half dozen I've tried it on.
As dumb as it sounds, if airplane mode is on, even if there is an active WiFi connection it won't unlock.
Boot to safe mode, turn off airplane mode, exit safe mode (restart) and it unlocks without issue.
Tested successfully on Galaxy Tab A & A7
Android 11
Meraki SM version 5.7.9 (2269)