(at around 1h 15 mins) Detective Crenshaw has just been knocked out by the Chain Man and is being dragged across the floor. They pass by an empty cabinet/display by the wall and you can see Detective Crenshaw's hand place or move something into the cabinet. A couple of seconds later his hand moves back up to his waist, all while he is unconscious.
(at around 1h 9 mins) When Neil is attacked, the hook is disengaged from the chain; in the subsequent scene it appears connected again.
(at around 1h 2 mins) When Jessie realizes she is being watched by the killer via her laptop webcam and on the killer's computer screen, it shows he is monitoring her by using GOM Player interface. GOM Player is actually a popular media player but not a live streaming or webcam tool.
At about 58 mins, Crenshaw's computer screen shows nothing but random letters and punctuation.
At about 47 mins, Rachel is still wearing her panties when she steps into the bathtub.