After sitting in the workshop for over 12 months, I pulled out this game and started to troubleshoot the niggling problems. It turned out that the issue with awarding 40 points instead of 50 points was to do with one of the switches on the score motor opening before the 5th 10 point point on the cam was closed. Really interesting problem. The coin issue was simply the switch was not adjusted.
After all this time, the game is playable and the clearcoat / touch up work looks the same at it was the day I finished it. Only one small problem with Player 1 not resetting the thousands scorereel every reset and I'm done !
It does not look like much, but this game is a fun game. Very addictive.