For whatever reason, I don't think you can trust the continuity checker, because it's saying the circuit is good, but obviously the power isn't getting through the player unit part of the circuit.
Instead, you can use your jumper wire as a probe to narrow down where the break is. Start by clipping one end of the jumper to the yellow wire. Touch the free end of the jumper to the red-black wire on the coil of the 1st player 10 point stepper unit. It should fire. Assuming it does fire, now you can use the free end of the jumper as a probe to check the rest of the circuit.
Next, determine which of the player-up unit wiper finger wires is attached to the blue-white wire coming from the 10 point relay switch. You should be able to do that by examining the solder lugs along the edge of the player-up unit circuit board, to see where the blue-white wire is soldered to one of the wiper finger wires. From your pics, it looks like it is the red wiper finger wire, but you'll want to double-check that.
I'll assume it's the red wiper finger wire for purposes of discussion. Make sure that the player-up unit is reset. Touch the free end of the jumper to the solder lug on the player-up circuit board where the blue-white wire is connected to the red wiper finger wire. If the score unit coil fires, there is a break in the blue-white wire between the 10 point relay and the player-up circuit board.
If the score unit coil doesn't fire, the problem is farther along in the circuit. Touch the free end of the jumper to the wiper finger attached to the red wire. If the coil fires, the red wiper finger wire on the player-up unit has a break, and will need to be replaced. If the coil doesn't fire, the problem is farther along. Touch the free end of the jumper to the pad on the circuit board that the wiper finger is touching. If the coil fires, the contact between the finger and the pad on the circuit board is failing. If it doesn't fire, the problem is farther along in the circuit.
In this way, you can continue to work your way along the circuit, toward the coil, until you get to a point in the circuit where the coil fires. Then you will know that the section of the circuit between where the coil fires and the most recent point where it didn't fire will be where your wiring break is.
- TimMe