Continuity mistake: After Mortimer picks up Elaine and literally throws her out the front door, he locks it to make sure she doesn't just open the door and walk in again. When Aunt Abby goes to open the door for Mr. Gibbs less than a minute later, she doesn't have to unlock it.
Factual error: There's a scene when Barbara Stanwyck hides behind an open door to avoid beeing seen by Edward G.Robinson leaving Fred MacMurray`s apartment. To make this possible the apartment door opens outside into the corridor, which is an elegant solution for this situation in the movie. But in the real world no apartment door would open by swinging into the corridor because this would give a visitor standing there a punch on the nose when the resident opens the door.
Continuity mistake: When the maid is out on the street calling a cab, the policeman shows up. The distance between them changes from close to farther away, between shots.
Continuity mistake: When the lodger is looking down the stairs at Daisy (who has just been handcuffed as a joke), his body faces the railing in one shot, the wall in the next, then the railing again.
Revealing mistake: Several pieces of furniture, including a large sofa, fall over before the suitcase bomb actually explodes.
Continuity mistake: Dick Powell puts his gun in his left trenchcoat pocket and then 2 minutes later takes the same gun out of his right pocket.
Revealing mistake: When we see for the first time cops fish out of the river one of Bluebeard's victims, the "lifeless body" helps herself up on the boat, practically climbing on her own. (00:02:15)
Continuity mistake: The postman walks into the tavern as the bell tolls. When he sits at the table with the others, everyone changed position at the cut. The bearded man had his hand on his glass, and now it's gone, and the priest's hand was not on the table, but then it is. (00:02:15)