ISSUE:
Backups failing with "An error was encountered while checking the system's disk/volume configuration and the backup cannot proceed. An unexpected error was encountered while getting the list of volumes - check the logs for additional details. The backup will not be able to proceed until the problem is corrected." error.
CAUSE:
The WMI (Windows Management Instrumentation) Writer is missing, stopped/disabled, or hung.
RESOLUTION:
Enable and start the WMI Writer in Services.msc console, and then re-run the affected backup job. KB: https://helpdesk.kaseya.com/hc/en-gb/articles/4407510090513-VSS-Writer-Failed-How-to-Restart-and-Re-Register-VSS-Writers