Continuity mistake: When Bulgy is driving on the road next to the rails, Thomas can be seen pulling a train instead of being repaired at the foundry.
Plot hole: When Duck and Diesel leave the shed, Diesel follows Duck instantly, but the tracks they are on both lead to the turntable. As they are on different tracks to each other, it would be impossible for Diesel to follow Duck that quickly as the turntable could only be set to one track at a time.
Continuity mistake: Despite Henry's issue from "Coal" in Season 1 being resolved after the crash in "The Flying Kipper", also in Season 1, Henry needed special coal again from "Thomas and the Magic Railroad" until Season 16.
Character mistake: The narrator says, "some trucks were left behind", but only 1 truck was left behind.
Bye George - S5-E7
Audio problem: Gordon has Duck's whistle sound before he crashes into the truck.
Visible crew/equipment: As Peter Sam passes Skarloey and Rheneas, a camera shadow is seen.
The Sad Story of Henry - S1-E3
Audio problem: When James is about to puff away from Henry's Tunnel, if you listen closely, James is heard puffing before he has even left. (00:10:00)
Other mistake: When Thomas is uncoupled from Annie and Clarabel, he has Percy's face.
James and the Red Balloon - S6-E15
Continuity mistake: When Percy arrives at the docks, he is carrying some freight cars. But when Thomas leaves the cars Percy was carrying disappear.
Visible crew/equipment: In the scene where James pulls up beside Gordon, studio equipment is visible in the top portion of the screen.
Continuity mistake: When Murdoch returns to the shed in the last scene, Emily is there too, but in the last two shots, she disappears.
Revealing mistake: Salty is missing his rear lamp in the first shot at the docks and a hole is visible where it should be.
Revealing mistake: Dried-up glue is visible around Rusty's face during the line, "Right, we'll find one tomorrow."
Continuity mistake: After Stepney's driver tells Stepney to speed up, Caroline is nowhere to be seen.
Visible crew/equipment: When the Fireflies form the engine, the end of the set is visible in the distance.
Other mistake: At the start Gordon's buffers are crooked.
Springtime for Diesel - S21-E1
Audio problem: Trevor has Stanley's whistle sound when he crosses the level crossing.
Continuity mistake: Thomas appears to be damaged and dirty after his accident but in the final scene, he is undamaged and clean.
Revealing mistake: When Toby asks Thomas if he took on enough water, Toby's eyes are wonky.
Continuity mistake: James and Edward are on the mainline at first, but then they overrun the platform at Dryaw station, which is on Thomas' branch line.
Answer: He was in the water.