The tracks skip backwards 1-2 seconds so the song repeats it sell, sort of like a stutter. But once it skips back, it will play through the whole song. The playback does not get stuck in a loop.
All tracks are mp3, and only do it on the player. If I play them on the PC there are no problems. I also can't get the same tracks to do it on the player, it sort of just happens when it wants to.