Ok, I'm stumped on this one.

Gottlieb Pioneer, 2 player version of Spirit of '76.
I've gone through and cleaned contacts but I think I might have made a mistake when I cleaned the player unit at the lower right corner of the head. There is a triangle thing to hold the piece on that rotates. I don't know how to figure out which position that thing should be on. (1 in 3 odds)
When I start a (one player) game, it plays ball one, then the next ball scores to the second player, then two balls that are scored on the first player, and then the next ball shows as ball 2 on the counter.
Obviously the machine is not selecting between one and two player games, and not selecting the ball correctly. It seems like the player unit is single stepping through, but since I don't have a book or schematics, I'm going in blind on this repair.  
Any EM techs out there that this fault sounds familiar too? If anyone has schematics and a book on this game, I'd be interested in a scanned copy.

Had something similar on mine but it is a williams system. You stated that you cleaned, what did you do?  Did you remove anything or simply just cleaning around?  Adding a picture if you can would help.  Furthermore, when was the last time your player unit was cleaned and your ball count spinner unit?  If you spinner don't reset completely at the beginning it throws everything out for a loop.

If I had to put money (1$) on this I would say you have dirty spinner units. I bet more as I get more info.....

take care