If I run the engine around the track I have no problems. If I use the engine as a switcher backing into sidings, building a larger train, etc, the engine stalls when and wherever I change direction. Sometimes it stalls on frogs. This I can take care of, but it stalls on good clean straight track. It doesn't matter what direction I am going when I stop, the minute I change directions, the engine won't move. I either have to give it a little shove or sometimes press down on it. I have cleaned the track and the engine several time making sure all points of contact within the engine are clean Everything seems in order and like I stated before - on the one direction run the engine never stalls. What am I missing. The engine was fairly new although it was an ebay buy. The only thing I have not taken apart to clean or inspect are the brushes.