There is a Linux kernel Bug from version 4.4.0-67 and newer that causes the Linux Kernel to generate Out of Memory errors and crash if the VM Guest is migrated live or backed up. Checking the Console you see many errors to this fact.
These 2 links document the issue:
KERNEL BUG
MICROSOFT FORUM
WorkAround
The Work around according to the Microsoft Forum is to remove the Virtual DVD drive from the Guest OS. This can be added when needed in future.