When the board is glitched or unresponsive, you can give it a hard reset:
Touch the main prim, but NOT on the player surfaces (where you move pieces or access the menu). Touch the root prim on the bottom or inner 'back' sides, and hold down the mouse button for approximately 20 seconds. A counter will start, and when mouse-down is continued for 20 seconds, a dialog pops up to ask if you want to reset the board. Select 'Yes'.