I had similar issue with not one but two Pandora boards at the same time. Both were fried. I put in my old Nelson board, and the marker worked again just fine except I need to up the debounce. Since the Excalibur that has the Nelson board is blind, I don't intend on changing out the board.
Barman is right; recheck with the Nelson board. If you have another AKA available, try the WAS board in it as a check.