At the beginning of this episode, Arthur is playing ping pong with Doug in the garage. The position of the garage door behind Arthur keeps changing between shots.
While Arthur and Doug are playing ping pong in the garage the first time, the spare tire beside the door under the window appears and disappears.
When Spence opens the door to the bowling alley, in the exterior shot he has pushed the door open. When the camera changes to the interior shot he has now pulled the door open.
After Carrie decrees a night of sex and George Foreman, the camera angle changes. In the next shot, the center window over the bed is being pushed shut by a crew member. Clearly it had been opened for the previous camera shot.