Watch app exit confirmation dialog always causes exit on Edge 540 (and I suspect other x40 devices)

I am implementing a confirmation dialog on exit, so capturing the escape key like this:

case Ui.KEY_ESC:
				var dialog = new Ui.Confirmation("Are you sure you want to exit?");
				Ui.pushView(
					dialog,
					new AppExitConfirmationDelegate(),
					Ui.SLIDE_IMMEDIATE);
				return true;
        		break;

Using this confirmation delegate:

class AppExitConfirmationDelegate extends Ui.ConfirmationDelegate {

	function onResponse(response) {
		if (response == Ui.CONFIRM_YES) {
			// If user confirmed, proceed with exit
			Ui.popView(Ui.SLIDE_IMMEDIATE);
		}
	}
}

It works in the simulator on all devices.

It works on some devices I have (e.g. 830 is fine) but on the edge 540 when i click the escape button to "CONFIRM_NO" the program exits anyway.

I believe this is a bug.