The sounds not loading after may come from the offline.appcache exported file (removing the sounds may help, but I think it is not the best solution)
The better way would be not to preload everything like that, but more preload just before you need.
I ve also saw that sounds seems to not stay on memory on mobile html, you could eventually try to play the sound in a silently manner, so it is actually in memory, then to restart it with a louder (audible) volume.
Also some phone (mine at least) refuse to play sounds for a reason, I think it needs sounds to come from a touch (which effectively sucks...), but my phone is a low end device that should not be targetted.I even wonder how my games runs at a 20 fps on it.