Fenix 3 input event handling

Hi, I have the following implementation:

class ViewBehaviorDelegate extends Ui.BehaviorDelegate {
...
function onBack() {
Ui.popView(Ui.SLIDE_UP);
return true;
}
...
}

I use this to handle behaviour on a View pushed by another View (i.e. a stack of 2). On the simulator, this works as it should - when I press the back button, 1 view is popped.

In the Fenix 3, 2 Views are popped. The only way I can make 1 view pop is by removing my onBack implementation. Am I doing something wrong here, or is the Fenix 3's View stack management broken? This does not happen in the Vivoactive device or simulator.