Continuity mistake: Gordon's express train has 1 composite coach and 2 brake coaches when he passes through Wellsworth station. When he crosses the viaduct, he has 2 composite coaches and 1 brake coach.
Factual error: When Bertie finds Thomas derailed, Bertie is on the wrong side of the road. The UK drives on the left. Also, Thomas runs under North American directional rules at the beginning and end of the episode.
Revealing mistake: Max's wheels can be seen moving backwards when he is actually driving forwards. Also, both Max and Monty's steering and wheel speeds are out of sync with their movements. These events happen throughout the episode.
Continuity mistake: Thomas appears to be damaged and dirty after his accident, but he is completely fine and spotless in the final scene. There is no way that Thomas was repaired and cleaned instantly.