For the last couple of weeks I have been getting: 'Backup aborted! - Unable to read from disk - Error Code 433 - A device which does not exist was specified.' on my scheduled weekly Saturday am full (followed by 6 daily diffs) backup. Same as this guy: https://forum.macrium.com/31511/Unable-to-read-from-disk-Error-Code-433 However if I then just run the full manually, it works, no problem. I have run sfc but nor chkdsk yet. Maybe try a new fresh definition with same parameters?