If I create a playlist in WMP and sync it no problems, if I then later add a single song to that playlist, and re-sync it, it resyncs EVERY song, even songs already on the device, by appending a random string to the title of the track. So I end up with trackname.mp3, F948WzF-trackname.mp3. etc. Meaning that after 3 or 4 syncs, I have to format and start again just to free up space wasted by all the duplicate (but renamed) tracks.
What is causing this, and how can I stop it?