Hi all, as per he topic subject, following upgrade to ATI2021 yesterday my nightly backup failed with 'Failed due to an error Unknown status'. The log (attached) seems to show VSS errors and 'A device attached to the system is not functioning'. I ran the VSS doctor which shows one error, insufficient disk space on the 'Windows RE Tools Partition of the C Drive. Get the same result regardless of target drive. Backup is of C drive to USB External and has been running without issue for several months. Ideas welcomed.