It's sometimes called the "stagecoach effect" from its appearance in old Western movies: If the frame refresh rate in your system synchronizes just right (wrong) with the (virtual) rotation rate of the wheel, it will catch frames (or between-frame renderings) that flash on in a sequence that makes it seem the wheel is going backwards. This is especially visible when the wheel has regularly- and closely-spaced spokes (like a stagecoach wheel).
The effect should go away when you change speed, though it may then reappear at other speeds. If it happens at *all* speeds, there may be an actual problem with the asset (the traincar) or, possibly, its configuration. In the configuration, it's possible to "tell" a bogey that it is running opposite the direction of motion; this is done when the bogey is turned 180 degrees by its attachment point, or by a position statement. This is an easier mistake for a creator to make than you might think, and harder to detect during testing.
So, check at different speeds - watch, especially, as the traincar starts to move, the first "reversal" is often easy to spot.
