Brainstorm

When Natalie Wood died near the end of principal photography, studio executives tried to kill the film and claim the insurance, saying that director Douglas Trumbull could not complete the film. However, Trumbull's contract gave that decision to him, and he insisted on completing it, using a stand-in and changing camera angles for the few remaining shots of Wood's character. The resulting hostility between Trumbull and the studio executives meant that this would be Trumbull's last Hollywood film. He has since devoted his efforts to effects work for IMAX films, theme park rides and the like.

There is no possible way that any assembly line could have been remotely programmed to have gone haywire and crazy at it did by Karen, and there is no way that a remote access terminal could override a direct power shutoff at the factory.

After the final credit has rolled, 'TO NATALIE' appears for a couple seconds

In the psychotic episode sequence when Michael's (Christopher Walken) son Chris (Jason Lively) wears the headset, there's a slight difference between the 70mm version and 35mm version. In the 70mm version of Chris's hallucination when Michael flips a lever presumably sending an electrical current to Chris's head, the camera cuts to and remains on a shot of a circular device with electricity running through it, as Michael is heard to say, 'Now you're gonna find out it's mine!' In the 35mm version, the shot arrangement is the same except that it cuts back to a closeup of Michael saying the line 'Now you're gonna find out it's mine!'

Edited into Trumbull Land (2018)