I've only experienced this problem with one band in particular, Agent Orange. When I add a track, it adds it to my library. If I click on "Artists" in my library, it says "1 Song". However, when I click on the artist, it shows two of the same song as being added to my library. I've tried adding multiple songs, and the same thing happens, two of each.
It's not a huge issue, but it's a little annoying when I'm trying to keep things organized.