Hi BogdanW,
It looks like that game is in great shape. Don’t give up, it’s a fun one.
As HowardR says, the player unit directs the score. If you moved it manually, it would go:
Player 1, ball 1
Player 2, ball 1
Player 3, ball 1
Player 4, ball 1
Player 1, ball 2
Player 2, ball 2,
And so on, until the game is over.
So, the possibilities are that either the player unit mechanism isn’t moving smoothly and closing the correct switches, or it’s not being told to move the right number of times.
A one player game actually has to pulse the solenoid 4 times to move from player 1, ball 1, to player 1, ball 2, etc.
I suspect that the 2nd problem is what you are experiencing, based on your description. I’ll check the schematic and see what I can suggest. The other great folks on pinside will probably beat me to it
Good luck,
Dave