Factual error: Black smoke comes out of Henry's cylinders, when it should only be coming out of his funnel.
Factual error: When Spencer brakes after he hears Percy whistle, his bogey wheels spark, but they do not have brakes.
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: 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: Breakdown trains help the engines back on track.