At about the 7 minutes 50 seconds, Poirot is seated speaking to Captain Hastings. For a period of about a minute, Poirot's mustache is obviously off center. The incorrect placement continues until he is standing next to Captain Hastings. It is askew again when Poirot first goes into Farley's office later.
While examining the room where Farley was found dead, Poirot opens a window. From inside the building, the window has hinges on the right side. A shot from outside the building shows the window with hinges on the left side.
In the first scene the clock in front of the factory is showing noon, but the hour hand is offset a few degrees to the left of the minute hand which is pointed straight up at twelve as it should be. At noon both hands should be perfectly aligned with the hour hand directly behind the minute hand.
Obvious stunt doubles at the end for Capt. Hastings and the culprit as they topple down a set of stairs.
During the factory's dedication, the actor playing the mayor can briefly be seen mouthing a line of one of the other actors.
The final scenes panning the local landscape, there is an abundance of modern TV aerials on buildings.
While Cornworthy and Hastings fight on the stairs, they push a big vase down which initially bounces off with a distinct hollow sound. A close-up follows when the vase smashes into pieces.
At 18:08 the clock on the wall's manufacturing date is visible: MCMLXXXVI (1986), but the story is set in the 1930's.
At the dedication of the new wing of the pie factory there is a shot from the lower floor up towards the people on the balcony. A woman worker is on the left side of the screen. A black gloved hand comes into the frame and pushes on her shoulder to adjust her position so she takes up a little more of the frame.
When Poirot finishes telling the board of directors Farley's dream, his daughter says he mentioned it to her and it upset him greatly. A couple of minutes later he asks her if Farley ever mentioned a dream to her and she says no which contradicts what she said earlier.