Can't unlock Macbook after sleep until powering off and on
This was happening to me as well with very similar error message. When I saw it was saying it couldn't find a display I tried plugging in an external display.. sure enough it turned on. I think this happens if the screen goes to sleep while plugged into an external display. Pretty awful bug. Note that I am testing it by plugging in the identical display.. not sure if another display would fix it.