The Bells of Saint John - S7-E8
Continuity mistake: Miss Kizlet wears a large silver brooch on her suit's right lapel in every shot of her, but after Clara notices the lights going out behind her house, when it cuts back to the office Kizlet's brooch switches to her left lapel just before it cuts back to the Doctor and Clara, and since the brooch has a distinctive design we can tell that it's a flipped shot. (00:25:11)