When the water crane has been sabotaged and the passengers have brought water to the engine, Mr. Valentine can be seen coming back to the train as the Squire gets back in the guard's van. In the next shot he is seen gathering the bottles he saved *before* coming back to the train.
When Dan Walker is handcuffed and on the platform looking at his house-coach, he has no pipe. As soon as he enters his house-coach he has his pipe in his mouth.
During the trial, the chimney on the saloon coach changes sides from right to left and back again in comparison to the Titfield Thunderbolt. The coach obviously was turned around during filming and pulled the other way.
When Dan Taylor and Walter Valentine are handcuffed, the handcuff is on Dan's left hand. When the coach driver and assistant are handcuffed to Dan Walker and Walter Valentine, Dan is now handcuffed on his right hand.
When Pearce and Crumps lorry breaks down on the level crossing the engine pushes it off the line but when the engine continues it's way the lorry is now upside down.
When Dan Taylor & Walter Valentine are driving the stolen locomotive through the town, the wheels of the lorry that the replica locomotive was built on can seen in a shot looking from behind.
In the last sequence, some men are playing cricket as the Titfield Thunderbolt makes its winning run to Mallingford. Abandoning their game, they rush to the embankment to see the train go by. The scene shows the batsman at the crease being distracted as the train appears in the distance, and being clean bowled as a result. However, although the bails on the wicket fall to the ground, the ball bowled by the bowler clearly sails more than a foot above the wicket.
When the locomotive is stolen from the turntable in the railway yard, it is able to negotiate the streets in the town and bends in the road out of town. This would not be possible as engines have no steering: the rails guide them and when cornering, there is a small amount of slip on the inside wheels. Even steering like a military tank (powering one side only) would not be possible as all the linkages and axles on the locomotive are fixed to drive together.
When Dan and Mr Valentine steal the locomotive standing on the turntable to run it away down the streets, the tracks covered over with grass are visible.
The close-up of the bishop and vicar on the right side of the footplate watching the arrival of the railway inspector is a reversed shot: the chain strung from the vicar's jacket and the bishop's hanging lapel are on the left and in other shots are on the right.
At the start of the test run they are concerned that the piece of rope will not hold between the engine and the passengers' coach. However as the train sets off we see a length of loose chain hanging from the back of the guard's van.
After Blakeworth throws his wet hat away it can clearly be seen on the track as the train moves away but a little later at the station he is clearly wearing it.
On the morning of the first run of the train in private ownership, Dan's blue alarm clock has no bells. They would normally be on the two stems connected by the carry handle, but the clapper strikes nothing. It still "rings" whilst traveling across the shelf due to vibration.
It never seems to occur to any of the villagers that the track would've had to be repaired before the inspector's train ran over it.
Sid James and the two men who suborn him are several times guilty of serious crimes against property in which people could have been hurt or killed. Yet, until the end, no one reports them to the police. Obviously, for the purposes of the plot, it is necessary that they remain free so they can cause more mischief, but it is bizarre that their actions are taken no more seriously than one side beating another in a cricket match.
When the policeman is reading the long list of charges from the top of his head, his eyes can be seen moving from side to side as he reads (most likely) from a list located just off camera.