Visible crew/equipment: When we see first Kate open a door, it opens, and she leaves her hand up, then slowly lowers it. Look to the left of the cube-shaped doorway, and you can see in the room behind her, the edge of a stand or table or some equipment, which obviously shouldn't be seen there.
Revealing mistake: When Kate decides to ditch Maguire and escape herself, we get a shot from above showing her face and Maguire's feet. However we only see his trousers. His feet are gone. Even though some could say that the wall removed them, but we can also see that the wall hasn't reached the part of the feet that are missing. It appears the CGI team forgot to add his feet in.