Ok cleaned-up that stepper unit, didnt make a difference. Moved on to the Q relay, and noticed one contact not closing to well. Adjusting this one contact set will make the problem better or worse, but finding the right adjustment seems difficult. Half an hour ago I had it perfect, machine behaved 100% for 2 of 5 ball games that I played. Then I left it for a few mins, played it again and the problem is back. Interesting that adjusting the Q relay also makes a relay in the bottom of the cabinet buzz more or less. When it is buzzing less the scoring problem is better. Definate link between these 2 relays.