by Ken Task.
Will backups work *IF* one removes the errant link to the non-existent file in the course? Moodle code only doing what it's been told to do ... backup, and include links to resource files (that's taken from meta data in the DB) and place those files in the backup.
Remove the errant link to non-existent file, then run the backup manually. Complete without error?
Question might remain, however, why/how was the file removed? Thought IF there was one course (hidden or active) that linked to a file resource, the file would never been removed.
'spirit of sharing', Ken