Continuity mistake: In the exterior front shots of Elliott's house there are some significant changes to the landscape in different shots. For instance, the two lampposts at the bottom of the driveway change to an entirely different style in some shots, and the huge garden boulders repeatedly vanish and reappear. Also, note when Michael takes off on Elliott's bike to go search for ET, the in-ground lamppost that should be beside the mailbox has vanished, but it reappears when all the government agents are setting things up outside the house.
Plot hole: Patrick Redfern needs someone to be in the boat with him to corroborate his and his wife's deception and be his alibi. That is whole point of his wife lying on beach - he gets this when taking Myra for a ride - but it was portrayed as a random ride she got, he did not intend or plan giving her a ride, he did not see her loitering near the boat, or even in view of him untying the boat. Even if that was intention in the story for him to be seen ready to cast off, the movie viewers did not see her viewing him, only her appearing just before he was set to cast off. Without someone with him the whole deception would not work, he would have no alibi, he could have killed Arlena unseen.
Factual error: In World War 2 London, Pink is shown playing with an aeroplane model - an Avro York. The earliest available plastic model kit of this aircraft was produced in 1967. Inaccurate model aside, it begs the question of what a kid of Pink's age would be doing with a plastic model kit during World War 2 anyway.
Continuity mistake: When the twins are singing about Brad for the talent show, and Michael was playing the piano (you have to listen and watch), his hands are suppose to go across the keys but he is still doing the fake up-and-down-hand-move.
Other mistake: When Deckard visits the Tyrell Corporation, he prepares to test Rachel with the "VK" machine. He is shown putting his briefcase of the table and lifting the "VK" machine out and onto the table. If you look closely, the "VK" machine is already on the table and Harrison Ford is miming the lifting - there is nothing in his hands! (00:19:45)
Revealing mistake: When the chair moves across the kitchen floor, Craig T. Nelson goes to investigate it (after it has stopped moving). He goes up to the chair and flips it over. If you look closely, Craig almost hits the camera with the chair's legs. You can tell this has happened because the camera moves up very quickly and Craig looks straight at the camera crew with very big guilty eyes. This is more easily visible on the widescreen version of the film. (00:33:30)
Factual error: I work for a television channel in 'daytime serial' production and I can assure you that no actor is going to secure a recurring speaking role in a soap opera unless a comprehensive insurance policy has been secured. (This applies to feature films, too.) This will inevitably involve a medical examination. I'm afraid Mr Dorsey's plans are going to become dreadfully unstuck the minute he drops his y-fronts in the doctor's surgery. (No, he can't find a compliant or bribeable doctor - the insurance company will always use their own people.).
Continuity mistake: When Brian Schwartz drives away in his sports car, you can hear him shift 4 times. When they show a shot of his car go by, he is only going about 5 miles per hour. (00:48:40)
Revealing mistake: In the scene where Chuck finds Bill in the morgue vault listening to the recording of Chuck telling him to shut up, take note of Bill's thumb on the rewind button of the tape recorder. You can hear the tape recorder rewinding to replay the words, "Chuck to remind Bill to SHUT UP" multiple times but Bill's thumb does not move at all until he turns the recorder off. (00:30:00)
Continuity mistake: When De Niro's character gets in the limousine with Lewis' character he has a hurt hand. He wraps it with a handkerchief. As the scene progresses the handkerchief disappears and reappears depending on the camera angle. (00:07:15)