The Snowmen - S7-E7
Continuity mistake: When the Intelligence in Simeon's body is attacking the Doctor, the Doctor's left arm goes from pushing at Simeon's right shoulder to suddenly stretched along the floor in a shot from above. (00:54:48)
The Snowmen - S7-E7
Continuity mistake: When Clara tests the solidity of the cloud the TARDIS is parked on, her right hand suddenly jumps to the railing of the staircase between shots. (00:18:14)
The Snowmen - S7-E7
Continuity mistake: When the Doctor offers Clara a TARDIS key, he's holding it differently between shots. (00:44:35)
The Snowmen - S7-E7
Revealing mistake: When the Doctor and Vastra are on the TARDIS talking about Clara's injuries, and he says that he thinks for once the universe owes him one, he pulls some switches on the console. If you pay attention, you'll notice that the console wobbles slightly as he does so. (00:49:48)
The Snowmen - S7-E7
Continuity mistake: While confronting Dr. Simeon in an alleyway, when Vastra picks up some snow and remarks about how interesting it is, the fingers of the hand she's holding the snow with change from being extended to curled up and back again between shots. (00:08:58)
The Snowmen - S7-E7
Continuity mistake: When the Doctor is explaining what the intelligence in the giant snow globe is, though enclosed, the amount of "snow" alternates from a fair mass to a few handfuls and back several times.
The Snowmen - S7-E7
Continuity mistake: As Clara first realises the differences in the TARDIS exterior and interior, she goes to circle the outside, leaving the door open. A second later, it's closed, but open upon her entrance.
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.