I was so frustrated the the engine was so erratic on the track that I just had to take the thing apart and find out what was wrong. When running the engine I noticed that there was an arcing sound that you could only hear if the engine was directly over your head. I found another broken wire to the front wheels that pick up power. So, I put a better wire in place and hooked it up. What was happening is that the large wheels on the engine pick up power and so do the little wheels in the front. The larger wheels move slowly on the track and had some buildup on the wheels. So, if you watched the train very closely you could see that when the wheel was turning, as it would get to the buildup, the train would pause and an arc would jump from the track to the wheel. This was making weld spots on the wheels.
So, I repaired the broken wire so that the front pickups (the primary ones) are again making contact, and I cleaned the big wheels. They are pitted from the arcing so they may be permanently damaged. With the little wheels picking up and the big wheels cleaned, the train runs smoothly again. The problem will return because the wires will eventually break again. The design of the carriage for the front pickups causes way to much movement in the wires and they eventually just break from being flexed so much. This is a bad design. I hope the new engine has a better mechanism for the pickup wheels.
If I were going to keep this engine for a long time, I would replace the wheels on the tender car with wheels from Aristo that have pickups. I did this for the performer car and the car runs much better. So, I could replace the wheels on the tender and wire the tender to the engine pickup circuit so that it had a better way to get power. I may still do that just to experiment after the new engine arrives.