I found out that on android tapping (clicking) on the loaded world space causes problem later with back-button.
Here are the details:
I use cordova app with angular 1.5. I have an Angular view with a button. Tapping on it loads (wikitude plugin v5.2) my AR world. After loading the world if I tap on the screen (let's assume there are no UI controls on it) and then click back button on my device, wolrd is closed properly and my angular view is shown again. But if I tap again back button on my device the app crashes (it goes paused and after resuming it starts at beginning with splash screen and etc.). If I don't tap the screen, or if I for example just move jQuery slider in world then everything is OK - no crash after tap back button and tap again in Angular view (the second tap). In summary this problems occurs only on UI controls which use onClick event - button for example. But even with empty world (<body></body>) clicking/tapping on the screen causes this bug. Yes it is bug to me.
If you are interested of the whole project I can send you for a cleaner look.