This is Mth 20-21309-1 GP38 Monongahela PS3. It became sluggish on its last run and wouldn't pull any cars. after taking it apart, it seems motor synchronization was off. The video shows what looks like no movement out of the front motor. Thinking possibly the front motor went bad, I replaced it with a spare of the exact same type, but no change. This is at a speed of 7-10 smph with no change in action. If i bump up to 20 smph then both motors kick in and it goes. As you can see, if I press on the rear truck at slow speed, it gains traction. I have also made sure my track is clean and I changed the traction tires as well. No change in action. Any help is appreciated. One of my favorite engines.