Factual error: During the surgical operation, Dr. Heiter makes incisions on the buttocks for the triangular flaps of connecting flesh; but the flaps are pointing outward, rather than inward. The only way to graft the buttock flesh to the face of the next subject would be with the buttock incisions pointing inward.
Continuity mistake: At the very beginning of the movie as the camera pans around to the parked silver Mercedes, the wheels are straight. However, as the camera enters the driver's window to show the Doctor, the steering wheel is turned to the left (note the control buttons and wood effect on the wheel are well out of line from where they would be if the car was going in a straight line).
Answer: Because back tracking they know what's around. They've already traveled that way and know it's passable and relatively safe.
Ssiscool ★
Thank you.