Does anyone know where to look for dirty contacts on the Gottlieb Baseball em machine that relate to it not recognising the game over when 5th ball is played. It is intermittent and sometimes it plays 2 extra balls- sometimes 7 or 8 times on the 5th ball. I dont have a schematic or know what to look for. It used to work fine then i stopped playing it for a couple of months. Ant help appreciated as i am wanting to sell it (Perth) but as usual with things, they play up when you want to sell and i would like to get it fixed before then.