Factual error: The aliens broadcast a series of pulses which are decoded by the scientists to be a longitude and latitude. In degrees:minutes:seconds, the longitude is 104:44:30 and the latitude is 40:36:10. These numbers are what the computer display shows and are what the scientists say (except for one slip-up in the hallway early in the scene where 104:40:30 is said). The scientists grab a globe and declare these coordinates are in Wyoming. Everybody and his brother (and the aliens) then proceed to show up at Devils Tower, Wyoming. However, Devils Tower is at around longitude 104 deg 44 min and latitude *44* deg 36min, not the *40* deg 36 min pulsed out by the aliens. If everyone had gone to 40 deg 36 min, they would have ended up in Colorado, more than a couple hundred miles south of Devils Tower, Wyoming.
Other mistake: In the climactic scene at the end of the movie when the alien mothership flies over Devil's Tower and the base, there is a shot of the mothership's shadow creeping along the ground, enveloping the shadows of the crew there. It's a dramatic shot, but since the mothership was not between the ground and the light source (the stadium lights of the base) it should not be blocking out the light, or creating a shadow.
Revealing mistake: The morning after Ronnie and Roy's big fight, Roy starts cleaning up his clay "sculpture." Before he pulls its upper portion off, you can see the pre-made seam (which is poorly disguised by the clay) where the top is attached to the bottom. When he tears it off, the lower portion is perfectly smooth and flat on top (simulating Devil's Tower) where it was obviously pre-cut.
Continuity mistake: When Richard Dreyfus has his first UFO encounter at the railway crossing, all the gauges in his truck go wild and the contents of the glove box comes flying out. After the encounter finishes, and the vehicle's power comes back, Dreyfus starts the engine and drives off. Miraculously, the interior of the truck has tidied itself and restored the glove box contents to their proper place.
Factual error: Early in the movie there's a scene that takes place at the FAA air traffic control center. As the film's other scenes are set in Muncie, Indiana, this ATC center is presumably (and correctly) in Indianapolis, yet, after the UFOs nearly collide with the TWA and Air East flights, the controllers are talking about "restricted area 2508". The "real" R-2508 is actually out in California/Nevada.
Visible crew/equipment: When the little boy is looking out the window of the farmhouse toward the sky to see the incoming spaceships (where he says "toys" rather excitedly), as the camera closes in toward him you can see the shadow of the camera/crane on the right side of the screen. The shadow changes as the camera zooms in.
Continuity mistake: As Ronnie backs out of the driveway, she knocks a Big Wheel across the road. She takes off as Roy falls off the hood and lands beside it. It disappears after he stands up and the angle changes.
Add timeMovie Nut
Factual error: When Barry first appears in the middle of the road, you can see the constellation Orion in the upper right of the scene. From mid-northern latitudes, Orion is visible in the evening from October to early January and in the morning from late July to November. The scene looks like a summer evening and if it was the morning Orion would not be that high in the sky.
Factual error: When Roy discovers that he has built a model of Devil's Tower as a result of an ABC news broadcast by Howard K. Smith, the remote reporter on site refers back to the anchor as "Walter" (Cronkite, as proved during Roy's interrogation), who worked for CBS, not ABC. (CBS did not allow Spielberg to cast Cronkite, and the dialogue was not redone to account for Smith).
Other mistake: When Richard Dreyfus rushes to the street to grab the trash can as the trash truck is coming down the street, his family is the only one on the block that has their trash cans out. It's obviously trash day and many of the houses are yet to be serviced by the approaching trash truck.
Factual error: Parts of the scene where the brightly lit alien mothership passes directly over Devil's Tower are shot with the camera looking almost directly up, as would be the view from the people below. In these scenes, Devil's Tower remains totally dark despite having this huge light source directly above. The mothership is so huge that a shadow cannot explain this darkness.
Add timeBruce Trestrail
Character mistake: When Ronnie is cutting the article about Roy's encounter out of the newspaper, the title of the article begins with "UFO's...", the apostrophe making it possessive. It correctly should have been "UFOs...", with no apostrophe making it plural as intended.
Add timeKit Sullivan
Continuity mistake: In the alien departure scene at the very end of the film, a solitary alien exits the mothership and approaches Francois Truffaut, who extends his right hand directly towards the alien and makes the Five Tones hand gesture. The camera cuts to another angle half-way through the gesture, and we see that Truffaut is now looking sharply to his right, over his extended arm, and smiling broadly at the alien as he completes the hand gesture. Apparently, Truffaut's body and extended arm pivoted 90° away from the alien mid-way through the 2-second gesture.
Add timeCharles Austin Miller
Continuity mistake: In India, Claude asks the Guru where the sounds came from, while a huge crowd walks along the desert. When a man in blue addresses the crowd to ask them, the crowd on the right side is gone, and the ones on the left aren't walking but standing perfectly formed like an army.
Continuity mistake: When Ray first arrives at Devil's Tower and stops the station wagon, the broken fence post resting on the hood changes positions between shots. In the view of him through the wind shield, the post is lying straight, parallel to the length of the wagon. In the next shot, it is suddenly at an angle, even though the car hasn't moved.
Audio problem: In the scene just as Roy, Gillian, and Larry take off for Devil's Tower, the army officer is on his car phone speaking to his superior. When his superior tells him if they don't get Roy and company off the mountain in one hour, to use EZ4. Lacombe, who was talking to David at the time, looks at the officer and says, "What's EZ4?". Lacombe should not have known what was said over the phone, as only the officer and we, the audience, knew what was being said. It wasn't a speaker-phone. [The army officer was using a VRC(vehicle radio console.) Not a cellular phone. The radio has a speaker mounted on the front of the console in addition to the speaker in the handset. So everyone would be able to hear the conversation on the radio. ].
Continuity mistake: Barry is leaving his house, going towards the trees. Jillian looks out her upstairs window and Barry as well as the immediate area surrounding him are drenched in bright direct light, as if from a spotlight mounted on the side of the house. However, from an outside angle of the scene he is not bathed in light, and neither is the area he is in.
Add timeKit Sullivan
Other mistake: One visual that has always bothered me that I could not find in your list were the scenes when the mother ship first appears. It's enormous scale appears to dwarf Devil's Tower and the whole surrounding area actually, but when it moves over to the "landing strip" area and begins to rotate 180° (right-side up?), it suddenly seems to shrink to a much smaller size and mass during the slow revolution. On its originally-seen scale above/behind the tower, one would think that either the great ship's outer prongs would have been torn off, or more likely the impromptu landing site and most of Devil's Tower would have been destroyed as the huge craft rotated itself. The visual scales just do not stay consistent throughout the film's climactic final act.
Revealing mistake: When the gigantic mother ship appears and sweeps over the rendezvous base at Devil's Tower, the camera cuts to look straight up at the advancing craft as it blocks out the starry night sky. Watch carefully to see some stars passing right through the leading edge of the mother ship, revealing a flaw in the traveling matte effect.
Add timeCharles Austin Miller
Continuity mistake: When Richard Dreyfuss is building the model of the Devil's Tower in his living room, behind him in the sliding glass doors you can see that it is raining, and when he turns around and walks to the door to look out, it is now sunny, and people are out side mowing the grass and children playing.