VSS: An unexpected error occurred when cleaning up snapshot volumes. Confirm that all snapped volumes are correctly re-synchronized with the original volumes.

Hi,

in my case the problem was the missing vss writer "system writer". when you run "vssadmin list writers" check if it's listed. If not, there are several possible solutions which can be easily found via google. In my case they all does not help and I eneded up, reinstalling the whole machine.

Also it's not a Symantec related problem because the cause it is the missing writer which comes from the Microsoft OS.

Best wishes & good luck.