I have a Southern in gold and green. (No such Mike ever existed as I understand on the Southern. I don't care.) Magnificent locos, and simply captivating. To scale?, not so much. But fun. Great smoke and sound. Big and impressive.
As I recall, and only that and not guaranteed, the first two rood names produced in the first run, UP and ATSF, had the defective star drive on the motor shaft ends.
later ones used a u shape connector which did not slip and eventually strip under load.
I added an LGB capacitor as I run analog and like the standing sounds.
I do not overload this loco, and on the flat pull about 8-10 cars.
Given current production, but Marklins practice of not supply spares, I would be careful to buy one in top condition only.