"There is a continuity error in the movie. See how the stack of PLI is facing left in this early shot."

It occurs to me that Arnold would be likely to turn these to face him when sitting at Nedry's desk (unless we see a shot of him going to sit and they already face forward). It'd obviously be part of the review of undoing Nedry's lockout to see if the backups are working (if I understand the point of the machines).