The "hardware" back button left of the home button just stops working as soon as i enter the app and the loading screen is done. It should do exacly what the back button in the top right does.
I dont know if its planned that way but its confusing since i'm used to the back button next to the home button working across every app and allways bringing me back a menu, and only your app is breaking that standard.

I hope this "bug report" makes at least some sense, its still early here....