Hi there. I have a 1970 Zip-A-Doo that interminttantly does not advance the ball. IT does this in single or double player and I cannot find a pattern to it. When it does advance, the pin makes a double click sound. I've read that if no score registers then it lets you replay the ball but I have registered scores and sometimes it still does not advance. I checked the Ball-Index-Relay and it appears to be working right. It engages each time that I register a score and it stays engaged. The tilt assembly on the side of the unit was disabled as well. It is designed so that you put a pinball in it and the ball slides forward and up to cause a tilt. I put a ball in there and simulated a tilt and it seemed to lock up the game. I took the ball back out and decided to tackle that issue separately but thought I would mention it in case the are somehow related. Any suggestions on how to troubleshoot this or where to start? I bought the schematic for it and I am just now starting to try and figure that out as well.