This has happened a few times, and I'm not sure what's causing it. This is happening on my incremental dumps, which only take about two hours to complete normally. What could be causing this to happen?

This particular run was done to a newly labelled tape, but I've seen it happen on tapes that have been in rotation for a while, so I think it's more dumper related than taper.

Here's the summary mail from last night's run.