Audio problem: Jonesy is playing the organ. A pigeon 'flies' out the top of the organ and lands on the keys, so Jonesy picks it up and moves it, taking both his hands off the keys. Yet the music plays on.
The King Was in His Counting House - S5-E7
Factual error: Captain Mainwaring is transferring money from his bank to another branch after it has been bombed. He has the money in a basket and is transporting it on a horse and cart when some of the money starts blowing out of the basket. Pike, Wilson, Walker, and Jones are riding bicycles behind him. They stop to pick up the money and just before Jones tells Pike to ride after Mainwaring to tell him about the money, you can see a silver car parked on the left hand grass verge in the direction Mainwaring is heading. This car was obviously made long after World War Two finished.
Continuity mistake: When the second bottle thrown by Pike lands on the floor, the glass from the first bottle has all disappeared.
Revealing mistake: When the knight moves back and forth during the clock mechanism's operation, as he swings his sword, a blue pullover sleeve is visible beneath his armour, revealing that he is an actor in costume and not an automaton.
Revealing mistake: The lights in the café are not working, despite the room being brightly-lit from above (i.e. the brightness cannot be attributed to sunlight entering through the window).
Other mistake: Wilson picks up the empty tablet bottle, but we hear the tablets rattling inside. Wilson then says 'it's empty, sir.'
Continuity mistake: At the end when they line up for The Royal Train to pass there are six platoon members amongst those present, Private Frazer is not one of them. However, after the train passes and they are shown wet in head shots, he is present. As the camera pans out, we are back to the original six.
Visible crew/equipment: Bank scene: As Pike is handing the mail to Mr Mainwaring, a boom microphone is visible at the top of the screen for a second, and is quickly removed from view. (00:09:10)
Factual error: The motorbike and sidecar used by the verger is a post-war 1945 BSA M21 with sidecar. The period is supposed to be 1942.
Revealing mistake: This actually happens throughout the entire show but is most obvious at the beginning of this episode: When they are in the churchyard it is obviously a studio stage, as there are shadows at all angles around the cast from the studio lights. Also, the lights are quite prominently reflected in Arthur Lowe's glasses.
Is There Honey Still for Tea? - S8-E3
Character mistake: When Mainwaring and the others are discussing how to break the news to Godfrey about his cottage, it is mentioned that the roof is made of thatch. However when Mainwaring, Wilson and Pike go to visit Godfrey, the roof of his cottage can be seen and it is slate, with no thatch anywhere in sight.
Is There Honey Still for Tea? - S8-E3
Revealing mistake: When Mainwaring first comes into the bank, followed by the workmen with his new door, behind them is the 'high street', actually a painted backdrop. This is normal routine for studio sitcoms, however Mainwaring and the others all cast shadows on the backdrop, revealing it as a studio set.
Come In, Your Time Is Up - S8-E4
Revealing mistake: In the very first scene Captain Mainwaring and Sergeant Wilson cast multiple shadows despite supposedly being in bright sunshine.
The Love of Three Oranges - S8-E8
Visible crew/equipment: At the end of the scene where Pike is setting up the stall selling the lampshades, a shadow of the boom mike can be seen on his forehead just before the scene changes to the auction.
The Making of Private Pike - S9-E2
Continuity mistake: In this episode, Captain Mainwaring was given a new staff car. However, he already has one from S7 E5, The Captain's Car. What happened to the previous one is never explained, and surely he would not lose all reluctance to accept the job if he already had a staff car?
The Making of Private Pike - S9-E2
Factual error: When Private Pike is on parade and keeps looking at his watch so he is not late for his date at the cinema, the watch is too modern for the period.
Continuity mistake: In this episode Mrs. Fox's first name is Mildred, but in "Mum's Army" (5-9) her first name is Marcia.
Answer: The show is a comedy, this was played for comedic effect and to show that in times of extreme fear, in this case about to be crushed by a steam train, the men had an adrenaline surge strong enough to pedal fast enough.