I had experienced a very strange problem: While listening to an album, I pressed pause at the start of the next song (and I made a long break in which I rebooted the device (Android 4.1).
After Restart the track was remembered and it played from the start (good!). After a while the lock screen came, and fb2k indicated the same song being played. After a very long time the same song was still displayed in the lock screen widget. So I unlocked and looked at the track list, and that also indicated the same track being played. However I was sure that the track being played is not the track being displayed.
So I exited fb2k, wiped in out from Androids app list and started it again. THEN the same track was played that I was listening at the very beginning, just as if the other tracks hadn't been played at all! (All my tracks are Ogg/Vorbis, created by myself)