End up all event, including press,click, hover is not working for the button at the edge, attached two screenshot. With the button 0 hover effect set to flat outline. u can see screenshot 1 when the mouse is near the edge of left hand side, raycast cannot be detected..while, when I move the mouse a little right, hover can be detected. (The screen capture cannot capture my mouse cursor, I add them back by photo edit. So just neglect the little color difference near the cursor, it just for indication purpose.) When I built it, button 0,4,5,9 cannot be pressed...