your stepper doesnt have a 6th position, so not sure how it figures is end of the game. again we need the schematic. Even a schematic of a similar age game could help. But it clearly isnt aligned properly if it can never get to the ball 5 position.
It certainly looks like it someone has altered it...! I don't think the chap I got it from has touched it, and he said it's always been like that (everlasting games) since he has had it (a number of years).
I hve a go at adjusting and properly lining up the stepper and let me know - I'm going to do some more research first, and hopefully my schematic will arrive soon as well.
Many thanks to everyone for their help and suggestions - I now have a working game!!! It was an incorrectly aligned ball count stepper unit coupled with a loose grub screw that made what I thought initially to be a fix, a little more inconsistant. It's all working correctly now, and I cleaned the contacts on the "Ball in Play" lights and changed the bulbs and they are all working now too (although they are very dim - does anyone have any suggestions for brighter bulbs (I replaced the originals ones with #47)).
You could try no.44s but if they are close to the backglass, beware of heat from these burning it. I avoid 44s because of that. If they are all dim, sounds like you have either all bad sockets ( common individually but not if wired in a daisy loop) or an earth issue. Try unsoldering one and connecting it with jump leads and crocodile clips onto something else on that line to see if it improves brightness And its not a bad idea to remove the Jones plugs and clean them to a bright finish.