Continuity mistake: Thomas was pushing 4 trucks and a brake van, but when the trucks are laughing at Thomas, there are 2 trucks and a brake van. A truck also gains a face.
Continuity mistake: After Thomas organized the trucks, he is facing the trucks, then suddenly he is facing away from the trucks instantly.
Visible crew/equipment: When Thomas races through Elsbridge station, you can see a hand drop in and out of the shot on the top right.
Continuity mistake: When Toby comes up to the junction, the lever to the points isn't actually there. It is only seen in this episode in the shot showing where his fireman switches them.
Fergus Breaks the Rules - S7-E18
Revealing mistake: A wire is under Fergus when he arrives at the smelter's.
Other mistake: When Oliver leaves for the Works after his accident, Toad's eyebrows are missing.
Visible crew/equipment: A crew member is visible on the left side of the screen when Skarloey notices the hot air balloon is about to crash.
Snow Engine - S7-E14
Other mistake: Before Oliver crashes, no-one appears to be inside his cab in a shot of him passing a crossing.
Thomas and the Runaway Car - S11-E17
Visible crew/equipment: When the flatbed rolls away from Thomas, you can see a finger of a crew member in the bottom corner.
Answer: He was in the water.