I have same issue with html5 game, but I don't want to update ios on Ipad (IOS 8 will fill my disk space ), same game works fine on iphone 4 with same ios version ios 7.1 and on other smartphones (android,windows phone etc) works fine as well.
Only on Ipad clear cache is only solution?
MIME types settings are OK on server.
I am trying to figure out where is problem and after removing sounds from game everything is fine.
m4a format is problem somehow
P.S. I am noob to all this and this is my first try to make html5 game