BRAND NEW to model trains. Purchased a ready-to-play set for easy entry. When the track is connected - the light at the power is solid. If I add any cars, the light stays solid. The moment the engine connects to the middle track, the power light flashes, signifying a short. I have confirmed that the wires under the engine are connected properly. I have even tilted the engine on the outside track and the light remains solid. ONLY when the center track connects with the engine does the power light on the track begin to flash. THOUGHTS? TIA