Deliberate mistake: In the PBS airings in the U.S. of "Tuneful Toots" and "Duncan and the Old Mine", Rusty is referred to as a female rather than a male.
Thomas and the Rainbow - S9-E2
Audio problem: At the beginning, Henry has Gordon's whistle sound.
Plot hole: When Gordon crashes into the goods train, it is not being pulled by an engine. So why is it just sitting on the mainline and not on a siding?
Audio problem: Gordon has a different whistle sound when he cuts in front of James at the water tower.
Character mistake: The narrator refers to Gordon as "Gordon's engine."
Flour Power - S9-E26
Factual error: The narrator says "Suddenly, Thomas felt something touch his tender," but Thomas is a tank engine. "Bunker" is the correct term.
Answer: He was in the water.