When the SWAT team breaks in the door to Marty's house, the door jam and striker plate remain intact after the door opens from being hit with the ram. The only damage is a nice round dent in the center of the door.
When the police are at the Walsh's house, the parents are sitting on the couch and the son is standing behind it. In the wide view of the room when the father goes to answer the phone the son is gone, and when the camera goes to a close-up of the mother gasping, he is back.