Send me the capx for that latest example. If you play the sound after you set the timescale to 0 then it will still play. So maybe that's where your problem lies. I did experience what you were referring to in that example.
Edit:
I recreated your capx. and added sound and music files and I got the same effect your experiencing. That's odd. I wonder if that's a bug.
What you could do is, set your master volume to something like -100 on pause and back to 0(normal) on unpause. Is that something that would work for what you are trying to achieve?