Hard Times - S1-E3
Other mistake: Crowley shows acute discomfort while inside the church with Aziraphale and the Nazi spies as he is on consecrated ground. However, (spoiler alert) once the bomb destroys the church he is perfectly comfortable. The key word here is "ground" - it is the land upon which the church stands that is consecrated, not the building itself. (This allows churches to be rebuilt if they are demolished or destroyed.) Crowley should still be in considerable discomfort after the church has been blown up.
Other mistake: When Harold goes to kill his father, we see his dad on the seat moving each time we hear the hammer, but if you look at his head, you don't see anyone hitting him at all.
Episode #1.1 - S1-E1
Other mistake: When Tony walks by the school there's a girl in a blue dress with a hula hoop that can't stop staring at the camera.