Had a situation with a VM that turned corrupt after been unfrozen. My feeling is this was the dreaded ODX issue.
The VM would boot and BSOD with Unmountable_Boot_Volume. Tried to mount the VHDX on the Hyper-V hosts and run a chkdsk /r but this wouldn't repair.
Veeam came to the rescue to recover the VM but the data was 36 hrs out of date.
We managed to recover the files by using this software.