When the surveillance man from the House Internal Security Committee picks up the large shotgun microphone, he switches it from his right hand to his left when he turns on one of the tape recorders. In the next shot, as he's still recording the message, the microphone is resting on the table and aiming a different direction.
When the grappling hook is first thrown, many scratches are visible from previous takes.
When the Mayflower moving van is leaving the parking lot to head for the rendezvous at the crime scene, several crew members (one of whom is holding a large reflector) are visibly reflected on the side of the van.