Hi,
Sorry, you post got a bit lost.
Current version is 5.2.3, I don't think there were any changes related to this, but anyways, pls upgrade to is to that we are on the same page.
Then, when you observer such situation, pls check Event log for a node that had SYS_NODE_UNREACHABLE event. Check Root ID column for this ID, is it 0 or not? If not, pls find event with that ID. Pls show screenshots