Also (although your symptoms are a bit different) a bunch of people have been experiencing frozen screens on their FP4 since the FP3 update, so you may also want to read and follow the following threads:
Additionally, there’s a thread about random FP4 reboots that occur since the update. It also seems like a different issue, but I’m not convinced it can’t have the same root cause. The guys over there have identified 5G as a likely common culprit. So maybe following that thread and experimenting with disabling 5G would also be a good idea: