Try TS Doctor to look at bad areas of the TiVo file. The 30 day trial is enough time to see if the TS Doctor works for you.Yeah, I've actually seen several times where combining them would be useful.
On the other hand, I've got it set to make 4 attempts and I usually get under 300 error packets, which really isn't that much (under 60KB), so I figure after VRD strips it out I barely notice it.
I think I'm going to modify my pytivo to save a better log file associated w/ each download (extension .syncerr.log) that will look something like:
Looking at log files like this should make it easier to decide if combining download attempts is worth it. Although as I said above, that's going to be trickier than I hoped.