When Nancy and Norman are sitting at Luigi's restaurant talking, the length of the candle goes up and down several times as the camera angle is changed.
When Norman first sits down alone at Luigi's, items on the table change position between shots. For instance, the bread sticks are first on his right, then in the next shot they are to his left.
Norman reads a newspaper article about Bonner's death, with a reference to a revolver found in Bonner's room. However, in the scene where Bonner is found dead, the gun that is beside him is a pistol, not a revolver.
American ambulances --- shown driven with left-hand drive --- were not used in wartime London.
Just as Mrs. Willis is putting the locket around Nancy's neck, her lips are clearly moving, uttering a phrase, but no voice is heard.
When Norman is looking for Nancy at the party and meets up with her on the second floor, the maid at the end of the hall opens the closet door twice.
John Willis reacts to Dr. Blair's story by calling it "libel." As an educated man, he should have known that libel is a written defamation, as in a newspaper story; the word he should have used is "slander."