If you're comfortable working on the game with the power on you can try to divide the circuit into two parts with a test lead. Figure out which of the two parts has the problem and cut that part in two and repeat the test. For example:
- Clip one end of a test lead to the white-red wire on the left side of your 2nd schematic above.
- Clip the other end to the blue&black wire on the 0 match light socket. This removes all of the switches from the circuit.
- The 0 light should light (just double checking here).
- Assuming the 0 light works you know the problem is in the other part of the circuit, to the left of the blue&black wire.
- Move one end of the test lead from the blue&black wire to the slate-green wire that leads into the match unit. That puts the 0-9 unit back into the circuit, but leaves out the X relay switch, the match adjust plug and a bunch of wiring from the circuit.
- Manually advance 0-9 step unit 10 times.
- If the zero light eventually lights the problem is between the white-red wire and the slate-green wire, or the part of the circuit you left out. Move the test lead from the slate-green wire to the white-brown wire and repeat the test.
- If the zero light doesn't light after 10 steps the problem is in the 0-9 step unit, probably with the way the connection to the slate-green wire is connected to the wipers.
/Mark
