I have a Bally Space Invaders pin, took out of storage and going over it. Machine boots up and re-setsifine, hit credit button, ball goes to shooter, and machine starts counting up (score) by 1000pts indefinitely. All other playfield targets seem to work during this. I have looked for stuck switches and have not found any, doesn't mean there isn't one...just haven't found it. Re-seated board connectors and looked for obvious problems, found none. Any suggestions would be appreciated, I'm new at this. Thanks in advance.