[Xanderfox]

The episode introduces "The Flesh" artificial biomass that is programmed to take the form of a human then is controlled remotely, the problem arises when the connection is cut off and the mind of the person is copied, the clones become copies with the same memories and personality as the original. Of course they are still made of "The Flesh" and until they stabilize can still stretch and morph a bit, getting highly emotional destabilizes the copies, so when the originals try to kill the copies yea they stress out. Add to that the Flesh copies the Doctor this is his 7th clone/copy I think, I know the 10th Doctor had a Human copy and ,a daughter/clone so it's at least the 3rd.