Moving House - S3-E1
Revealing mistake: At the beginning when Frank is directing the vans, we see that one gets its windscreen broken by a ladder from another van. However, the glass breaks just before the ladder touches it.
Wendy House - S3-E2
Revealing mistake: When Frank is talking to the postman at his front door, it's so obvious it's a studio set. The background seen outside the front door is painted scenery.