Closing the app is the problem ...
From the Manual
'Browser '
On suspended
On resumed
Triggered when the page's visibility changes, or when a mobile app is going in to the background or foreground. When invisible or in the background the app is suspended: all events stop running and all audio is muted.
As you can see...all events stop running when the app is invisible or in the background...
AS far as I know you cant change this...its a hard coded feature...
The only way I know of ..is to keep the app memory...