Audio on iPhone - distortion after a minute of soundtrack & still playing when browser closed

Hello,

In my game, which I play in the Safari browser on an iPhone 5, I get audio distortion about a minute of play after the soundtrack has loaded. There's also a delay before the soundtrack gets played, and I set it to preload the audio in the left panel of Construct 2.

So after a minute of the soundtrack playing it start distorting and then stops. When I close the browser, the sounds (even the soundtrack) still play for a few seconds as well.

Any idea what I can do to fix this? Or is it iPhone related?

Thanks.