
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.
Thomas, Percy and the Squeak - S6-E21
Continuity mistake: When Percy arrives at Brendam, his steam platform is visible and some of the steam from his funnel disappears, indicating a film cut.
Continuity mistake: Henry pushes Percy onto the coal tipper twice.
Gordon Takes a Tumble - S6-E17
Continuity mistake: The amount of trucks Gordon is pulling repeatedly change.

Gordon Takes a Tumble - S6-E17
Continuity mistake: When Gordon leaves the docks, he has his lamp, but in the next scene, it disappears.
Answer: Breakdown trains help the engines back on track.