I solved the issue probably. I always had the PCG partitioned option On.
The PCG workflow for partitioned PCG Volume works way better if you cleanup everything from the volume, make any changes you want to the PCGActor (like changing the partition cell size, remember that any change to cell size quadruples number of PCG operations (divide cell size by two = 4x more partition squares)) and after the changes generate the volume again. Generate on Demand option is good, so is “Pause generation” in the PCG graph.
Using this workflow almost eliminated the bug in this thread.