When partyshuffle starts and it has a mix of mp3 and m4a songs (itunes and wmp as player) you get weird things.
When you skip manually to the next song the correct song is actually played, but the list is not updated.
This means that the MP1-2 song of the list is playing and MP1-1 is still standing.
After the song is done MP1-2 will move to MP1-1 and will start playing again.

This results in hearing the same song twice.