Instance crashes and locks up networking on NAS

I migrated a Windows 11 instance which was working for a couple of days but then it crashed.

At the same time I lose all remote communication to the NAS but via the console I can see that the server is up and I can restart and everything is fine again.

I replaced the mobo a few weeks ago before upgrade to Fangtooth. The old mobo was Intel with Intel NIC but the replace had a realtek NIC. Under EE and the old VM architecture the VM was fine but under Fangtooth it seems to crash.

I suspect it is the NIC so I am going to replace it with a PCIe Intel card.

Can anyone please advise if there are logs I can check to see if the networking went funny so I can confirm my suspicion?

Thanks