I think people may be thinking of the music commands here. As far as I know stopping a sound is easy, it is music that is more of a blanket thing.
jump=loadsound("jump.wav")
jump2=loadsound("jump.wav")
playsound(jump,100,1)
playsound(jump2,100,1)
do
if getrawkeypressed(32)=1
stopsound(jump)
endif
Sync()
loop
This plays two identical sounds which I have loaded into separate ID's. I then proceed to stop the first sound when pressing space. Works fine, the other sound is still playing, but you can easily hear the other has stopped.
Music on the other hand, works differently, as there is no ID in the stopmusic() command.
I may be missing something, as I have only skipped over the thread, but I'm not sure of the issue, at least on a PC. On android etc, there are several sound issues, or at least there where.
Edit - Having looked at the thread more in detail, I think I see what the issue is. Only way I can think round it is to perhaps have several ID's made that it can count through. So say 10 for example of each sound. So each time you play the sound, it moves to the next, and then loops back when it goes past 10. Pity there isn't a clone sound command to reduce memory usage and loading time though. it is a cheat but would work I believe.