hmm you have a problem, which I admit would be terribly frustrating. there should never be anything being over written .. and even if they were the exact same name, they would be imported anyways because they have different track numbers. You can have thousands identical track names (some jazz albums have three takes, usually indicated in the tag, but not always.
I believe you would need to have album artist, album name, track no and track name to be identical .. probably the artist field too. I suppose it is possible that the tag information is bad, but that would mean that the track numbers would have to be the same too at the very least. That would be very rare.
Perhaps you have set-up incorrectly your ripping masks (template)? Perhaps you have set up your import options incorrectly?
could you open the tag window and copy and paste here the File name with the path for one of the track for the bach album in question
(I have four different versions of Bach's Partita No. 1 in B Flat Major - the eighth part is always Gigue, the first is Praeludium there are 3 minuets I suppose, but even if they were just Partita No. 1 they still have different track numbers).
Explaining how the JRiver db works takes longer to get into (no unique record ID per se, its not relational), but I have never seen this happen.