Factual error: A "wonky" whistle doesn't sound like a slide whistle, it should sound like a weakened version of the correct whistle mixed with the hissing sound of steam. A "wonky" whistle would also leak steam constantly instead of being blown like a normal whistle.
Factual error: When Spencer brakes after he hears Percy whistle, his bogey wheels spark, but they do not have brakes.
Factual error: Black smoke comes out of Henry's cylinders, when it should only be coming out of his funnel.
Factual error: In the U.K. narration, when Flynn sees Gordon, the narrator says "Flynn steamed in to a stop." but Flynn isn't steam powered. This mistake is fixed in the U.S. narration.
Answer: Butch the breakdown truck must have pulled Gordon's tender all the way up the rails so the breakdown train can reach it and also Butch helped to get Gordon close to the winch.