I'm having some difficulty with my Star Trek Next Generation pinball machine. There is a feature of the game that causes balls to become "locked". Whenever a second ball has become locked, the machine keeps trying to fire a new ball into the playing field even when one is already in the playing field. It just makes a loud thumping noise as its trying to kick a new ball out to be shot. When the ball in the playing field eventually gets lost at the bottom, this ball is then reshot into the playing field...so basically, the game never ends...it just keeps shooting balls out. I only have this problem after a second ball has been locked. Has anyone encountered this on their machine and is there a quick fix? Thanks for your suggestions!!