Continuity mistake: After Nardole gets Pictish facepaint, the lines change in consistency and exact positioning several times throughout the episode.
Continuity mistake: When the Captain's arrival at the South Pole is first shown, walking up while Twelve is explaining to One that the frozen snow means something is very wrong with time and asking if either of them is a doctor, to which Twelve responds, "You trying to be funny?", the two Doctors are standing right next to each other. When the Captain's arrival is shown from his perspective, however, the Doctors are standing much further apart when Twelve says the line. (00:09:00)
Forest of the Dead (2) - S4-E9
Continuity mistake: When the Doctor realises that the Vashta Nerada infesting the Library came from the books, he rubs the back of his head with his right hand, with his left hand in his trouser pocket. When Other Dave speaks, and the Doctor turns to him and discovers he's been eaten, he takes his left hand from the back of his head, with his right hand in his pocket. In the shot after that, his left hand is back in his pocket with his right hand in position as if he'd removed it from the back of his head. (00:18:30)
Continuity mistake: When the Doctor and Nardole are being held by the Picts in a circle of weapons being pointed at them, when Kar's brother points a knife at the Doctor and warns him not to speak until she gets back, his arm is almost fully extended in shots from above and facing the Doctor, but much more bent in shots facing him. (00:12:40)
Forest of the Dead (2) - S4-E9
Continuity mistake: After the Doctor tints Anita's visor, as he explains to River that he did it to try and trick the Vashta Nerada into thinking they're already inside Anita's suit, the position of his right hand, holding the sonic screwdriver, and the fingers of that hand change position between shots. (00:10:25)
Continuity mistake: When Bill unwraps the mirror Alit got her and holds it up to look at her reflection, she raises it so the top of the mirror is above her shoulders, then it cuts to a close-up where the mirror is suddenly lower. (00:16:35)
Continuity mistake: After the Doctor tells Bill that nothing gets through the TARDIS doors, when she responds that they're made of wood and have windows, the Doctor's left hand changes position between shots from being apparently by his side to suddenly resting on the door. (00:28:40)
Continuity mistake: When the Doctor holds out his sonic screwdriver for the Dalek to scan, his grip on it changes between shots. (00:42:25)
Continuity mistake: After the Doctor and Bill are tied up in the tent of explosives, when Lord Sutcliffe pulls out his pocket watch to check the time and notes that the elephant is being brought onto the ice, in a shot facing the Doctor and Bill the watch chain is taut. When the shot cuts to look at Sutcliffe and his henchman, the chain is slack. (00:33:40)
Continuity mistake: When the Doctor picks up a skull from the bones waiting to be ground into fertilizer, the position of his hands holding it changes between shots facing him and shots looking at the skull. (00:15:10)
Continuity mistake: When Bill says to the Doctor, "Do what you gotta do," he raises his hands to her. His hands are closer to Bill's face in shots facing him than shots facing her. (00:48:40)
The Return of Doctor Mysterio - S10-E1
Continuity mistake: When the Doctor pulls a glass of water out of his pocket and hands it to Grant, it jumps from his left hand to his right between shots. (00:05:05)
The Unicorn and the Wasp - S4-E7
Continuity mistake: At the lake, when the Doctor stands in front of Agatha and tells the Vespiform, "You're not meant to be like this! You've got the wrong template in your mind!", in the close-up shot he has his left arm raised, but in the Vespiform's POV shot he has his right arm raised. (00:39:45)
The Unicorn and the Wasp - S4-E7
Continuity mistake: When Robina Redmond is announced, and Lady Eddison says, "She's the absolute hit of the social scene - a must," in the first shot, Lady Eddison is standing close enough to her wheelchair-bound husband to cast a shadow on him. In the second shot, the distance between them has suddenly increased. (00:05:10)
The Unicorn and the Wasp - S4-E7
Continuity mistake: After questioning the houseguests, the Doctor and Agatha are talking. She uses the phrase "little grey cells", and the Doctor responds, "Oh, yes, little grey cells. Good old Poirot." When he does this, he's holding a saucer in his left hand and rests a teacup he's holding in his right hand atop it, as he turns toward the chair that the suspects were sitting in. In the next shot, as he walks over and sits in the chair, he is suddenly holding the teacup and saucer in his right hand, with his left hand in his pocket. (00:13:55)
The Unicorn and the Wasp - S4-E7
Continuity mistake: After the Doctor opens the Unicorn's case of tools, his right hand changes position when Greaves enters the room to deliver drinks. (00:22:20)
The Unicorn and the Wasp - S4-E7
Continuity mistake: After explaining that he's laced the soup with pepper, the Doctor, when he says, "Anyone got the shivers?", turns his head from looking to his left so he's looking in front of him. In the following wide shot, his head is turned to his left again. (00:26:10)
Continuity mistake: When the Doctor starts scanning the wall of the tunnel as Jenny asks him who he is and if he's an anomaly as well, his grip on the sonic screwdriver changes between shots. (00:22:20)
Continuity mistake: After the Doctor opens the secret door in the tunnel wall, he puts the sonic screwdriver into his inner jacket pocket. In the next shot he's in, as he says, "Now, what were you saying about running?", he does it again. (00:22:55)
Continuity mistake: When they get out of the TARDIS at the beginning, Martha and Donna change positions relative to each other between shots. (00:00:55)
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.