I've had my cabinet now for several months, using a keyboard hack for the interface... and I am just now finding a blocked key that I missed!
My 8-year old daughter would complain that she sometimes had trouble moving when she played King of Fighters or Sailor Moon with a friend, but I thought she was just losing and complaining about it...
Recently, however, I re-discovered Robotron, and that brought out the problem in a hurry... down'left or down-right on Player 2's joystick blocked down on Player 1's joystick! A quick trip to GHOSTKEY and a little probing, and I found a different key to swap in... had to re-compile Stella to account for the change, too....
I'm just amazed I could have a control fault for so long without noticing it!
--Chris