Plot hole: McKittrick says the computer will not accept the launch codes unless they are at DEFCON 1. At the end of the climax the computer is trying to guess the code while they are at DEFCON 1. So why couldn't they just go back to a different DEFCON before the correct code was guessed?
Plot hole: Bond would not have had (nor taken himself) time to lay a complete and careful clown make-up while changing clothes in the circus trailer.
Plot hole: George Lebay says that his brother died "6 weeks ago" inside Christine and that's why he's selling it. Later that evening after Arnie leaves his house and goes to Darnell's, Will Darnell says he "knew a guy who owned a car like that" and "the bastard killed himself in it." If it's only been 6 weeks since his death, shouldn't Darnell have recognized the car? It's not like there were lots of red Plymouth Furies (custom order color) running around the small town, let alone the USA, even in 1978. (Also considering how production even had a hard time finding them for the movie).
Suggested correction: He says he knew a guy with a car like that. It doesn't have to be the same colour or even the same generation. Just a Plymouth Fury.
Darnell basically said he knew THE brother of Lebay, not just some guy who owned a similar car. Darnell described Lebay's brother based on the story. Again, it was him, not just some other guy.
Plot hole: The police let Norman back to his house on the same night multiple murders happened. He is even allowed into the fruit cellar, where most of them happened. (01:38:25)
Plot hole: All those years in the spy biz as U.N.C.L.E.'s very famous top agents, and Solo and Illya are still able to successfully go undercover with little or no disguise. Here, all Illya needs is a phony mustache and an even phonier accent. And of course (gotta love it), the Thrush bad guys still don't recognize him. (00:49:00)
Plot hole: The demonstration to the Board of the system's potential is ported through acoustic modems. Even in those days (early 1980s), anyone would have realized that the bandwidth simply wasn't possible at 300 bps.
Plot hole: It seems unlikely any mental institution would let a patient out to visit home for any length of time as happens in the movie with the killer and his mother.
Suggested correction: Unlikely, but still possible. Almost every workplace has a situation in which a person is bending the rules.