Visible crew/equipment: Near the end when Montag arrives at the Book Peoples' commune, he is greeted and ushered into a house. There's a shot from just inside the building, looking out a window towards Montag and his host as they approach. As the POV shifts a little, a reflection of the camera becomes plainly visible in the window glass.
Fahrenheit 451 (1966)
1 visible crew/equipment mistake
Directed by: François Truffaut
Starring: Julie Christie, Cyril Cusack, Anton Diffring, Oskar Werner
Deliberate mistake: Montag's hair gets intermittently shorter, longer and shorter again (and acquires a "cow lick" that wasn't there before) near the end of the film. (Oskar Werner had clashed with Francois Truffaut and deliberately had his hair cut to spite director.)
Guy Montag: To learn how to find, one must first learn how to hide.