[rdiff-backup-users] Error: "File changed from regular file before signature"

[Randall Nortman]

I'm running rdiff-backup 0.12.8, because the system I'm backing up is
pretty ancient and I just haven't been motivated to upgrade it yet.  A
while back, one of my backups was interrupted, so the next time it ran
rdiff-backup had to regress the archive, and encountered an error:

Previous backup seems to have failed, regressing destination now.
Warning, metadata file has entry for var/spool/exim/input/1FQbbR-0007NJ-00-J,
but there are no associated files

Now, every time I run the backup, I get this:

UpdateError var/spool/exim/input/1FQbbR-0007NJ-00-J File changed from regular
file before signature

The rest of the backup works normally.  The file these messages refer
to no longer exists on the source system -- it was obviously just a
temporary file in Exim's queue.

I'm not sure where to look for this in the metadata.  Presumably, I
need to find it and delete it manually?  Or would this be handled
better by a newer version of rdiff-backup?  I'm willing to upgrade, I
just need a good excuse.

Thanks,

Randall