Continuity mistake: At the beginning they show a close up of Jason, the skin around his eyes and ears (around the outside of the mask), are flesh colored and looks like normal healthy skin. When Adrianne takes his mask off during the autopsy they skin is grayish like it's decaying.
Continuity mistake: When Rowan is stabbed by Jason she slides down to the floor and freezes sitting up. She remained undiscovered and undisturbed for over 400 years until the scientists find them. So how did she end up lying on her back covered up by what look like exhaust tubes? Aside from the unlikelihood of no-one stumbling across her for all that time.
Answer: Jason wasn't deformed as a child. Jason was deformed at birth. His regeneration can't fix anything better then it already was, just to where it was to begin with, therefore since his face was always deformed it can't be fixed better than its deformed state. If half his head is blown up it will regenerate, but only as far as the deformed state.
oddy knocky