When Jack pulls the doorbell box off the wall above the door, it's obvious the prop box was just hanging on a nail. The wires aren't connected to anything.
In the opening scene when Mr. Furley is attaching the new doorbell chime, there are no no screws in the wall while he uses a screwdriver.
When the girls are showing off their swimsuits to Jack the camera pans too far left and the end of the set is visible.