When Arkwright appears from the alley with the dog he has borrowed, there is a blue van in the background. In the later shots of this scene, the van disappears in the closeup shots of Arkwright, but reappears in the distant shots of Arkwright. This happens 2 or 3 times.
When Gladys grabs the top of the ladder to prevent Arkwright falling, the outside wall wobbles as the ladder makes contact with the wall.
When Granville opens the door after leaving with Maureen and Eric, the backdrop outside looks like the backyard, rather than the street.