Example: play a song that allocates FM0 for a track, then play another song that allocates PSG1.
Expected result: FM0 should be stopped
Actual result: FM0 is not stopped
A solution can be to always wait one frame before starting a track (or request slot) if another is occupying the track slot.
This is semi-fixed by 2d912a7f22de9f7656c55f59c7ddc0e8187a6f5c, although not completely - it just stops a previous track on that request slot, if another request slot happens to use the tracks requested, it will not stop those tracks.