I lean toward the switch points being the issue as described in the video Chessie1971 posted. My guess is that the motor is pressing more weight over one truck than the other and the heavier side of the engine is want to keep moving in the direction it is going. If it turns out the switch is not the issue, however, it may be that the wires from the truck pick-ups are binding somewhere and limiting the movement of the truck. I've seen this on some other older engines, but not so far on any LC/+.
JGL
