Continuity mistake: When Salty gets blocked by the trucks, his face increases in size.
Saved You! - S12-E10
Continuity mistake: After he is rescued by Thomas, Toby's face changes size between shots.
Gordon Takes a Shortcut - S12-E15
Audio problem: Stanley has a different whistle sound. His original whistle sound is essentially Thomas' at a lower pitch, but in this episode, it is Thomas' at a higher pitch.
Thomas Puts the Brakes On - S12-E17
Continuity mistake: Thomas has a brake van when he arrives at the bridge. When Stanley, Thomas, Murdoch, and Rocky start looking for the bricks, the brake van disappears.
Thomas Puts the Brakes On - S12-E17
Revealing mistake: When Stanley shunts Thomas into the yard, Thomas is eyeless.
Thomas Puts the Brakes On - S12-E17
Revealing mistake: In the very last shot of the episode, Thomas and Stanley are faceless.
Other mistake: The narrator says that Thomas' driver puts syrup in the lion, but actually, Thomas fireman puts the syrup on the lion. This is identified by his moustache.
Character mistake: The narrator says that Thomas had never delivered the mail before, but he did in Season 4.
Other mistake: Mavis and Cranky should've realised that Thomas woke them up the first time he blew his whistle.
Continuity mistake: Thomas says that Mavis and Cranky never make mistakes, but they have in "Mavis" and "No Sleep for Cranky."
The Biggest Present of All - S13-E16
Audio problem: When Henry and James are at the quarry, their whistle sounds are played out of order.
Continuity mistake: After Thomas goes to the docks, the giraffe's flatbed somehow changes tracks at the Animal Park.
Other mistake: In the first shot of Brendam Docks, there is a siding that is inaccessible from the other tracks.
Factual error: Black smoke comes out of Henry's cylinders, when it should only be coming out of his funnel.
Continuity mistake: When Thomas finds Percy, he is behind him; but later when they arrive at the Steamworks, Thomas is in front. The same thing happens with Edward.
Factual error: When Spencer brakes after he hears Percy whistle, his bogey wheels spark, but they do not have brakes.
Continuity mistake: When Thomas passes Gordon, Butch's magnet is attached to Thomas. In the next shot of Thomas, it isn't. And in the shot after that, the magnet is attached again.
Audio problem: When Thomas and Butch deliver Rosie's wheel, her whistle sound is at a higher pitch.
Continuity mistake: Gordon's Hill is much taller and steeper than it usually is. Also, when Belle reaches the other side of the hill, the tracks on the viewer's left disappear.
Factual error: A "wonky" whistle doesn't sound like a slide whistle, it should sound like a weakened version of the correct whistle mixed with the hissing sound of steam. A "wonky" whistle would also leak steam constantly instead of being blown like a normal whistle.
Answer: Breakdown trains help the engines back on track.