When scoring, is the ones score reel moving the correct number of turns, but the tens digit is not being pulsed? there is a 9 position switch that is supposed to close when the score reel is on 9... if you look at the reel there should be a small label that shows the position of this switch. On the tens digit reel, I believe there is also a switch that is part of this circuit. If either one of these switches is misadjusted, that could cause your issue... report back if you can tell which switches I am talking about/and if you see the score reel sticker I'm talking about.... sometimes these stickers fall off over time, especially on old Williams games.... but there should be one on at least one of the reels.

Don O