I have bought a new Fleischmann 4-4-0 with tender drive and low speed running is very jerky. Medium speed running is fine. The pick up is fine as I can see the wheels moving between jerks forward and the valve gear seems smooth enough when rotating the driving wheels by light finger pressure. I have run it for an hour each way at various speeds without any sign of improvement. Each jerk forward is about 4 sleepers worth. A few questions.. ..Is this a known problem with a known solution? Are all Fleischmann 8 wheel tender drives the same as i would not want to buy another ? Do I just send it back ?..probably about $100 worth of postage 2 ways. Would like to hear any advice or comments.