The sensor boards are interchangeable, but the wire lengths are different. You can run the CGo3 wire directly from the pitch arm to the gimbal board (without threading it through the frame) to see it it cures the problem.
Of course, first make sure everything is plugged into the proper connectors, none of the existing wires are damaged, and all the solder joints are good.
A continuity check with a multimeter will show if any wires/solder is actually broken, and it can show if there is a short between wires, or from wire to frame.
Sensor boards do sometimes go bad, but it's pretty rare. It is far more common for the issue to be damaged wires or connectors out of order. If two plugs are reversed, you would expect to get two codes, but that does not always happen. It sometimes only sounds one code, and not the other. You can also use the multimeter to ensure each encoder is plugged into the correct board connector.
