vRanger 6.1 cannot perform an FLR on any archives in a given CIFS Repository. The error occurs on the mount phase, where the archived volume(s) fail to mount to the vRanger machine.
Directly share out the Repository as a different, non-hidden share name (i.e. "V" instead of "V$").
Remove the old Repository, leaving the savepoints intact.
Recreate the Repository (this will not prompt for an "Import" or "Import as Read-Only", etc., since the Repository location/Globalmanifest file has not changed).
Run the FLR again.