I have the same issue.
There are something interesting in my case.
My unraid server usually crash and bring down the whole network during weekly parity check.
I use 1G switch in my network. When the unraid server crashes, the whole network is down. I think it's a 2-layer problem instead of 3-layer, because other device cannot ping each other in the same network. Once the unraid server is unplugged, network restores. If I plug it back, the network will instantly crash.
Anyone got any ideas? It really drives my crazy:(