When the loan officer is shot down, the papers strewn around him are television and radio servicing schematic diagrams. The symbols for tubes can be clearly seen. Red writing on the page says "1 meg" which is a resistor value (electronic component).
The assassin's weapon is a J&R Engineering M80 Carbine, which would never be used as a sniper rifle since a carbine's short barrel provides inferior long-range accuracy compared to a weapon with a much longer barrel.
During the closeup shots of the car radio during the first news broadcast, the gearshift is in the park position and the key is in the off position despite the car being driven.
Obvious stand-in for Murray Hamilton (much younger and with straighter, darker hair) when Dr. Cooper drives into the gas station at 15:41.
Two tape recorders are used for the mission briefing; holes are visible under the take-up reel on the second one for the smoke when the tape self destructs.
When Adele Cooper (Madeline Rue) is driving away in the delivery van from her house Dr. Cooper's Cadillac convertible is seen parked in the street even though it is actually supposed to be at the service station with a bad radiator hose where he is being held hostage.
The policeman responded to the cafe with his emergency light and siren. He then drove away using his emergency light and siren. Police typically only use their emergency equipment when there is a confirmed emergency.
Barney's "caller ID" should identify the numbers from left to right, rather than in a random order.
When the helicopter lands on the roof of City Hall (50:45) numerous movie production trucks and mobile dressing rooms are visible on the streets below.
When Dr. Cooper (Murray Hamilton) is getting into the helicopter near the end of the episode, several crew members are briefly reflected in the helicopter's swinging door.