So, actually there was a bug, but it only happened when you destroy something that was still processing events. In this case, you click a button and that removes a view that contains it, so that exposed this 2 part issue. First was a bug in haxui-core and second was in hxWidgets. These should be fixed now - so you’ll need git versions of each lib (lemme know if you dont know how to do that)
All in all a great find!