Have you tried doing a move data on this tape?

I have often found that if the tape has some sort of damage to it or a
damaged file or a left over fragmented space, that a move data clears this
up - because many of the times, it is not actually data on the tape it is
fragments that were left behind from a previous move data - that is why we
now use reclamation instead of "move data" - but we are still cleaning up
our tape pool and I have found that many of the old tapes still have this
problem - thus, I do a move data and it clears it up. The next time the tape
is reclaimed, I do not run into this problem - not even with the new tape
that it wrote to. :0)