[PostgreSQL] ERROR: LargeObjectDrop: large object

You tell us. All that message says is something called lo_unlink()
with a parameter that's not the OID of any extant large object. If
you have application code that's in the habit of doing such things,
then it isn't a problem; otherwise, it might be an indicator that
you've got bad data or who knows what...

FWIW, I doubt that the version update has anything to do with it.

regards, tom lane

If he did a dump/restore, might it be possible he didn't properly
transfer the large objects?

Robert Treat