Visible crew/equipment: When the trucks are pushing Toby, in one shot you can see a crew member's hand pushing the trucks, then it vanishes.
Edward, Trevor and the Really Useful Party - S3-E16
Visible crew/equipment: When Bertie is talking to Trevor, in one shot of Trevor, studio equipment is visible in the top left hand corner.
Revealing mistake: While the passengers are evacuating the station, the platform moves, a pillar in the background moves, and putty can be seen on the platform (stains of it) and on some passengers' feet.
Other mistake: When Bill and Ben are pushing each other, Bill has no eyes, Bill and Ben's faces are slanted at the bottom, and Ben's cylinder pipe is crooked along with a tack above Bill's face seen.
Other mistake: When Oliver leaves for the Works after his accident, Toad's eyebrows are missing.
Thomas and Percy's Christmas Adventure - S3-E26
Audio problem: When this episode was re-narrated in the US, it was changed to an episode about Thanksgiving. This caused a scene to get cut, which messed up the dubbing track, making half of the episode out of sync. (00:03:00)
Audio problem: Gordon had Duck's whistle sound and James had a different whistle sound in almost every Season 4 episode they appeared in.
A Bad Day for Sir Handel - S4-E6
Revealing mistake: When Sir Handel derails, you can see a small rod sticking up out of the ground from the tracks.
Peter Sam and the Refreshment Lady - S4-E7
Other mistake: In two shots shown at the beginning, Henry is wearing Gordon's upset face mask.
Audio problem: In the US version (Rusty Helps Peter Sam), Peter Sam has a different whistle sound after the trucks hit him. And throughout the episode, a lot of music and sound effects are missing.
Revealing mistake: When the passengers lift Duncan back onto the rails, his trailing wheels are still derailed.
Visible crew/equipment: As Peter Sam passes Skarloey and Rheneas, a camera shadow is seen.
Character mistake: On his way back to the sheds, Sir Handel goes through a red signal.
Audio problem: Thomas has James' whistle sound when he passes Sir Handel at the beginning.
Revealing mistake: Dried-up glue is visible around Rusty's face during the line, "Right, we'll find one tomorrow."
Continuity mistake: When Rusty arrives on the Other Railway, chains are seen hanging beside the signal box, but in the next shot when Rusty asks, "Ooh! What's that?", the chains have disappeared.
Audio problem: Stepney's whistle sound changes throughout the entire episode. And in the UK and other versions (excluding US), Gordon, Duck, and Douglas have the same whistle sound.
Continuity mistake: After Stepney's driver tells Stepney to speed up, Caroline is nowhere to be seen.
Bowled Out - S4-E18
Continuity mistake: When the diesel grinds to a halt and the camera switches to Duck and Stepney and then back to him, he is noticeably further away from the coaches.
Bowled Out - S4-E18
Audio problem: When James leaves Crovan's Gate, he has Smudger's whistle sound.
Answer: He was in the water.