You have native Hyper-V Replication set up: the VM is replicated between 2 or more Hyper-V hosts
You back up the replica machine (VM2)
You perform entire VM recovery from this backup into original replica machine (VM2)
After recovery, the previously enabled Hyper-V VM replication is now replicating changes from VM1 inconsistently, since it assumes that VM2 (replica) has state different than the one it is after recovery.
You are trying to back up a Hyper-V virtual machine which has virtual disk with an ampersand (&) in file name, e.g. Docs&Users.vhdx. Backup fails with the following error: