Blue screen (Ntfs.sys) on Windows Server with Hyper-V host, replica and backup on NAS Server.

Question

Hello. I have several servers with Windows Server 2016 and Hyper-V installed. Each has several virtual machines with Windows Server. Each virtual machine has a replica of another physical server and a backup of the NAS server, which is made overnight. Since some of the virtual machines are small in size, 60-120GB, I decided to make the backup of Hyper-V virtual machines on a dedicated disk on the NAS server.

After about two weeks of normal operation, one Sunday morning at 5:50 am the physical server on which Hyper-V is running stops working and a blue screen appears with an error Ntfs.sys. After a restart, the same error again. I used to run the last good configuration and the physical server started. I managed to start the virtual machines, but the one that had a backup constantly gave a blue screen.

I decided to start the replica. It started, but the moment I added a network card, a blue screen appeared on the virtual machine again with an error Ntfs.sys. When I removed the network card or it was enabled, but without the IPv4 protocol, everything worked. The moment I added IPv4, and again a blue screen.

I decided to use the backup. But when I mount the iSCSI to Windows, a blue screen appears with the same error. I tried on several computers and they all crash the moment I mount the iSCSI disk.

So the virtual machine, its replica, and backup ended up being corrupted. I had to reinstall Windows Server and set up a new domain controller.

I couldn't figure out from the information in the logs what the reason was and left things as is. After 6 days, however, the case repeated itself with another server on which there is a backup of a virtual machine on a NAS server in exactly the same way. Absolutely the same blue screen on the physical server with Hyper-V. The replica gives a blue screen when adding a network card, and the backup freezes every computer that connects to it.

I have stopped these backups for now because I am sure it will happen again. My questions are as follows:

1. Is the failure caused by backing up the virtual machine from the Hyper-V host?
2. Is the failure caused by backing up to a dedicated hard drive?
3. The new virtual machines that replace the two damaged ones do not activate Windows. This is a software problem and I should not have to pay for new Windows licenses.

Thanks.