Regeneration.

Whenever Christine repairs herself from being damaged, it's always done when she's sitting still and more specifically after she's come "home" to Darnell's. This is completely opposite from the book, in which as soon as her victim(s) are dead she begins undoing the damage. During the drive back to Darnell's, that's when she would fix herself. Even after Repperton's crew almost destroyed her, it was Arnie literally pushing her around Darnell's junkyard until bit by bit she had been restored enough that she could drive again.