When Marci escapes from the web in the elevator shaft, she closes the door on the spider chasing her. In that sequence, the door closes automatically; in other scenes, the door opens and closes manually.
When Marci, Jake and slick discover the dead nurse's body, Marci is shown wearing her glasses for one shot, but they were broken in a previous scene.
When the man spits in Marcie's face, there is a shot of her glasses hitting the ground, but look carefully and you can see the glasses by her neck in the next shot.
The floor indicator lights in the elevator are not consistent. In some scenes, the numbers go up as the elevator descends (as if to indicate sub-levels), while in others the numbers go up as the elevator ascends.
When Marcie and slick fall down onto the spider's web in the elevator shaft, their bodies cross each other, but in the next shot, the are on top of each other.
Reflected in helicopter's front window.