Corrected entry: After Mrs. Connelly says, "Could you sprinkle some salt on the steps, they're terribly icy," Alex says his line and walks out without closing the door. After Alex slips and is lying on the stairs, the door is closed without anyone there to close it.
Corrected entry: Mrs. Connelly gives Alex a Bugle that she dipped in onion dip, but in the following shots the Bugle is no longer covered in dip.
When Alex shoots the harpoon and the old lady is returning to her apartment, Alex puts back the harpoon on the mantle and the rope of the harpoon is neatly folded back up. He wouldn't have had the time to properly do this by the time she returned.