When Wanley is hurrying back into the apartment through the rain, his hat and coat are clearly soaked. In the next shot, when he is inside, his clothes are considerably less rain-soaked than before.
When he is taking the "dead" body out of the car, the "corpse's" eye opens and closes.
When Claude Mazard hits Alice in the face, his hand clearly does not actually hit her, yet she reacts to it.
When Alice Reed runs to house after the death of Heidt she simply pushes the door that would be closed and needs a key to open.