I took a look at our install quickly, but didn't see anything obvious. It is probably nothing you are doing.
I would bet that it is an issue in the upgrade scripts, and if you submit a ticket to support, they will be able to fix it for you.
We had all sorts of issues upgrading from 6.0->7.1->7.5, at each step. Usually support was able to give us a fix for it within a day or two. I think that at this point we are out of the woods until we try doing our production system anyway. :)
The end result of this issue was HP providing some SQL to resolve the issue. The SQL was provided almost instantly, so I expect others have had the same issue. I've attached the file and the instructions provided.
FROM HP: Please copy the attached script 'tm_work_units_750_1.sql' to '\upgrade_750\750\postseed\tmg\' And overwrite the old script and restart the upgrade again.