Wendy House - S3-E2
Other mistake: When Frank, Betty and the insurance assessor are sitting on the sofa, it's obvious that all three actors are trying hard not to laugh when the assessor starts sinking into the sofa.
Jessica's First Christmas - S2-E7
Other mistake: When Frank open his front door to Mr. Jackson the walls around wobble.
Other mistake: The walls of Frank's house wobble whenever he opens the front door.
Other mistake: As Frank and Betty move the wardrobe a chair tips over by itself. Frank and Betty are nowhere near it - it is presumably attached to a wire which is pulled by one of the crew, but has no significance to the plot.
