I still experience these issues, have they been fixed at some point during the last year?
I had a lot of trouble with sounds on iOS while developing a game, and it seems to be a problem with the appcache and m4a files for me as well. On the first load of the game, audio is (mostly) ok, but after that I have very little but mostly no sound at all. When using the preview over LAN feature audio works just fine, but it seems that it doesn't cache files there.
I also tried to produce the same error with the SpaceBlaster demo, and made a 2 minute recoriding here:
Sometimes the sounds disappear just by refreshing, but I can get the error every time if I open the demo in another tab, or by closing the tab and opening the demo again.
I found this, but don't know if it relates to this issue:
Clearly it is a iOS bug more than it is a Construct 2 bug, but I would really like to understand why caching audio on iOS is a problem.
(sorry about the crippled urls, but this is my first post, so I can't submit links)