This loco runs exactly 2/3 of the way around my 8x8 layout and stops in exactly the same place each time (on a straight track, not a curve). It still has power (headlight works) and a gentle push gets her rolling again but she stops at the same place each time. I have run a Niagara, UP FEF, and SP GS-4 on the same tracks with no problems. I have also tested her operation on a roller track and she runs flawlessly. What do you think is the problem?