I have an older Bachmann GP35, DCC on Board, with the vertically split frame. The loco goes about 5 or 6 feet, then stops for a couple seconds. When it stops, the headlight goes out. Then the loco starts up again and a couple seconds later the headlight comes back on. This happens often going around the layout. I've reprogrammed a couple times but doesn't seem to make any difference. Question is, is this a mechanical problem or electrical? Maybe bad connection or bad decoder?