Michael is trying to shuffle his playlist using RhythmBox, but it keeps playing artists back to back. Leo says that if the playlist is small enough, it could end up doing that, but if it's a large enough list, it is more likely an error in its random number generator. It's open source so it's probably just faulty code. Amazon Play seems to do the same thing, though. Unfortunately, there's no real fix for it other than filing a bug report and waiting for a fix.