Try reheating all the header pins on the board itself. Make sure the optic is okay and one of the 4 legs is not partially broken off. Also, the interconnector board between the backboard and the game (on the LEFT WALL inside the game) is LOADED with cold solder connections....reheat this board---it seems to solve lots of problems.
I am sure you checked to make sure wheel is spinning evenly...we ha a motor shaft slightly bent, and when wheel spun, the part that blocks the optic for half of the revolution, was actually moving out of the optic path! Todd Tuckey from TNT Amusements