Visible crew/equipment: When Bob comes home and sees that Ann had been in his garage, - he walks into the kitchen via the door, but if you look at the walls, you can see the darkening shadows of the crew and equipment.
Revealing mistake: When Bob Crane was playing drums in the club, the night that he told Patti he and John were going out - he CLEARLY isn't playing to the beat, as you can hear drum fills, and he just playing as hitting the drum once with his left stick.
Other mistake: In the scene in the KNX broadcast studio, a shot from the engineer's point-of-view shows VU meters with their needles not moving, even though Bob Crane is talking.