I think you have a choice to either contact Kato to see if they will take it back for repair, or take it apart yourself. I think we have probably done all of the trouble shooting possible on line. Since the problem is only in one direction and only on one locomotive, the problem would appear to be internal on that locomotive and not track related. I have one more question, how many lights do you have going forward compared to running in reverse? If you have headlights, ditch lights, a mars light, and gyro lights when you run forward, but only a head light when in reverse, you may have too much lighting load for your throttle, particularly in dc. When the ho modular club used to run dc with blocks, some of the members locomotives with sophisticated lighting packages used to require twice as much throttle for half of the speed of models running without lights.