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.
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.
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.