Generally when you click or tap a button on mobile devices and then don't do mouse-up or lift touch on the same button and do it elsewhere the action is cancelled.
But the Phaser buttons don't behave like that. Do the mouse-down on the button, drag and do the mouse-up outside the button, the button-click is still triggered.
Is there a way to fix/change that behaviour?
PS: I just tested that when you use the event.onInputUp on sprite etc, it is still fired when the onInputUp happens outside the object.