I have similar issue that others. The BG music starts, but the Sounds - in my case these are narrations - do not first time. In my stroybook the first time a page is displayed, the narration not starts, but the second time.
I would like to ask if there is any lenght/size limitation of the sound files? I'll try to preload the sounds...
My narrations not play trought the end, but for about 10seconds.
I have 130-250 FPS... :)