So if you can place the car on inspection from the controller, you can test to see what isn't working. Does this work and the top of car not? Is ins1 and 2 dropping out? Are you getting 125v to the inspection buttons? Are you getting 125v to the main up or down main reverser circuits from the inspection buttons? If you say that indeed H D DM (DX?) in then you will have to check the volts going to the levelling field circuit.
