I have the same kind of issue on stable with the backported kernel 5.10.19-1~bpo10+1: black screen after resuming from sleep. It happened with kernel 5.10.13-1~bpo10+1 as well. The warkaround I found is to put down the lid, wait a little bit and reopen it one more time. No need to reboot. It has never failed for me.
The issue is indeed somewhat random (it's KO around 50% of the time).
