Continuity mistake: At the beginning, Missy is using a knife to sharpen a stick to a point. Later in the scene, when she says to Clara that if they go rescue the Doctor, everything the Daleks can throw at them is between them and him, she lists only the stick among their assets. The knife is never seen or mentioned again after Missy was done with it.
Continuity mistake: When Clara takes Rigsy's chronolock, in the closeup of the tattoo Clara's lifting her hair with her right hand and showing the tattoo with her left hand, but in the next front-facing shot her hands have switched, she's holding up her hair with her left hand and showing the tattoo with her right hand.
Continuity mistake: When Bonnie throws the laptop with the Osgoods' message to the floor and stomps on it, the computer's position changes between shots - take note of the tape markings on the floor. In addition, the position of the plastic frame of the laptop's screen changes: in the first shot, it's mostly popped out, but in the second shot, it's mostly attached.
Continuity mistake: For most of the robbery sequence at the beginning, the Nightmare (a disguised Ashildr) is holding her pistol in her right hand. When she's yelling at the Doctor for interfering with her robbery while he's looking at the chest strapped to the back of the carriage, however, she's holding it in her left hand. It switches back to her right after the carriage escapes.
Continuity mistake: When the Shade leaves Clara and she falls, her body is twisted because of the way her legs are bent with one on top of the other and her arms are out to the side. In the overhead shot of her, her positioning has changed, her body isn't twisted and her arms are more straight down her side.