When Mike Raven (Fabian) is playing the piano, his bow-tie is untied. However, when the others are examining the record player, he is shown pacing in the background with his bow-tie tied. In the next shot, it is untied again.
Early in the movie, the characters hear a tape recording accusing of them of murder. Later, however, when Lombard makes a reference to Blore's crime, Blore responds with a surprised, "Who told you?" when he knows exactly how Lombard found out about it.