Hyper-V VMs get hosed after backup

"Hosed" being the technical term.

It seems that after either/or of 2 VMs on the host machine, after a backup, cannot start.  It also appears that Backup Exec creates snapshots that don't get re-absorbed into the parent virtual disk.

So I'll end up with a series of .avhdx's, and if I try to start that VM, it'll tell me there's an ID mismatch in the chain of virtual disks.  Pretty much every single time after a backup.  The exact error is:  

'VSERVER' failed to start.

Synthetic SCSI controller (Instance ID XXXXX): Failed to Power on with Error 'The chain of virtual hard disks is corrupted.  There is a mismatch in the identifiers of the parent virtual hard disk and differencing disk'.

There is a fix, using the Set-VHD command, but I can't keep doing that over and over again.

Additionally, I'll get this error from Backup Exec itself:  V-79-40960-38691 - Backup Exec cannot create a recovery checkpoint for the 'VSERVER' virtual machine.  (Note:  "Use snapshot technology" is checked).

Any ideas where I can start looking to fix this?

Backup Exec version 21.4, 1200.2536, Windows Server 2019

Thanks!