When Julie makes tea for Elizabeth it shows Julie throwing away the tea bag. When she gives the tea to Elizabeth the tea bag is obviously hanging out of the cup.
When Elizabeth catches up with Julie and they start fighting there is a gun between them then suddenly the gun is gone.
When Elizabeth tries to open the sliding glass door, she pulls the wrong direction (she would be closing it). When she uses a barbecue spatula to break in it is obvious that that door could not be broken into in that way.
In many scenes it is highly obvious when a doll substitute is being held in lieu of a real baby - the "child's" face is hidden, he is impossibly stiff and his body and limbs sit unnaturally.