Despite the explicit dialogue and written appearances of the name that make it clear that the character Scott ffolliott has no capital F, the name still appears as Ffolliott in the end credit cast list.
The establishing shot of the Hotel Europe is actually an outtake from the later rooftop escape sequence. Haverstock can be seen on the far left edge of the frame, next to the neon letter "H", crawling across the roof, although he is still in his hotel room at this point in the story.
In the chase scene at the windmill site the aircraft circling is in two scenes a single-engine, single-tail, high-wing type, and in a subsequent scene it suddenly becomes a twin-engine, twin-tail, low-wing aircraft.
When Johnny and Carol step down from the taxi in front of her house, he takes the suitcase with her left hand and changes it to the right one, to direct her with the left hand. After the taxi leaves, he is holding the suitcase in his left hand.
When Johnny first comes across Van Meer in the windmill,his raincoat is closed and tightly belted. He reaches into his lapel pocket to get out a pen,but never undoes the belt. When he moves away from Van Meer after hearing the men on the stairs, his belt is all the way undone,and his raincoat is loose.
When the "fake" Van Meer is murdered in Denmark, his assassin, with camera in hand, can be seen running from the steps into the crowds, in a long shot. In the next closeup jump shot, he's still on the stairs, before running off into the crowd for a second time.
Despite being an ingenious camera trick at the time, it's an obvious mannequin dummy being dropped out of the window after ffolliot's fight in the hotel room where Van Meer is being interrogated. George Sanders' character falls through the awning that breaks his fall at a completely different spot from where the dummy lands.
The name of London's famous Carlton Hotel is spelled correctly on the two telegrams addressed to Haverstock that are shown onscreen. However it is misspelled on the cap of the doorman who opens the door to the cab for Van Meer, incorrectly written as "Carleton".
In the church tower, Rowley lifts a boy to give him a better view of the city and the boy's cap is blown off by the wind and falls to the street. Later when the boy and his friends leave the church they all have their caps on, including the one whose cap was blown away.
As the Purser on the ship tells John and Carol that he has no more cabins, the right side of his fake moustache can be seen sliding down. He surreptitiously pushes back in place, but as they turn back for a second try and he continues speaking, the moustache slides down again.
During the scene where the passengers are scrambling to get out of the sinking Clipper, a man grabs a suitcase and smashes a window, leaving a lot of large, jagged pieces of glass in the frame. He then climbs through the window and sits directly on the jagged glass.
When ffolliott stops his car outside the mill, he keeps moving the steering wheel as he was when the car was moving. The rear projection has stopped, but he is unsure and keeps pretending to steer.
[Note: the character's name is spelled with no capital initial.]