Thank you very much, I see an interesting crash report in your logs:
USER ERROR: Condition "slot >= slot_max" is true. Returning: nullptr at: get_instance (./core/object/object.h:972)
This is 100% the cause of the crash, though I cannot cause it to happen on my PC consistently. Apparently, it has something to do with a known bug in Godot 4.0. I will try to use one of the workarounds I found in the documentation and report back.
Did the crash happen mostly between scene transitions?