Factual error: The movie starts in 1985, jumps '5 years later' and then back to Sasha Luss, then '3 years earlier'. So, in her crusty apartment in an impoverished neighbourhood of 1987 Soviet Russia, Anna is filling a form on her notebook-style laptop, too modern for the era. It looks like a NEC UltraLite (considered the first notebook style laptop) which didn't even come out until 1989, let alone the likelihood of someone in the USSR having one.
Factual error: While handling the ignition coil cable to the distributor cap, Joe Pesci tells De Niro that the timing chain needs adjustment in his truck. A truck of that year with an inline Chevy motor would not have a timing chain at all, instead this truck would be equipped with a direct drive timing gear. Even if it had a timing chain, it would be behind the water pump and a cover. It would have been a several hour job to replace, not possible to adjust it.
Factual error: Based on the films being shown at the theater, the movie appears to be set in 1981. One of the TV commercials shows the Energizer Bunny, which didn't make its first appearance until 1988.
Factual error: It is not possible that Pitt could have gone up to the ship when it was already blasting off. There was literally fire in the tunnel.
Suggested correction: It was a bit confusing, but what I saw was a shower of sparks or hot particles and some fumes, and no fire in the tunnel until he was through the hatch. The makers may have been influenced by seeing vapour prior to a rocket launch, and then some rockets use a shower of electric sparks to ignite the engines. It was implausible, but no fire in the tunnel.
Factual error: Throughout the movie, scenes of the chess tournament room show the American flag incorrectly vertically hung (stars on blue upper left is proper), while the Soviet flag is correctly vertically hung. No real American vs. Soviet tournament would make that mistake.
Factual error: Opening the blank envelope, Marta finds the fragment of the toxicology report. It is signed "Office of the chief medical examiner, Norfolk County, Massachusetts." But then it writes also the address of said office, which is in Marlborough. Marlborough is also the city when Marta resides, and where the lawyers' letters we see come from. But Marlborough is also a city in the Middlesex county, not Norfolk. (01:28:25)
Factual error: While in Hong Kong, they show several shots of Singapore.
Factual error: A plastic bucket is seen. Plastic buckets were invented in the 60s. (00:50:05)
Suggested correction: There's no plastic bucket seen. If you're referring to the bucket cops are using at the crime, there's a shot of the bucket on its side and you can tell there's a metal bottom.
Factual error: There's a flashback to 1989 in an arcade and we see Mortal Kombat and Mortal Kombat II there. The original wasn't released until 1992, and the sequel in 1993.
Suggested correction: Subtract 27 from 2019 and you get 1992. They were 12-13 in 92 so it is plausible that those games could have been in the arcade while they were still kids.
It's set in 1989, not 1992.
The "present day" scenes in this film actually take place in 2016, 27 years after the first film is set which would be 1989. The mistake is valid.
Some of the flashbacks seem to be set after the first movie.
That flashback definitely was not supposed to be after the first movie, it featured Henry Bowers.
And Pennywise would have been asleep in 1992~1993 so that whole scene after the arcade makes no sense.
Factual error: Like so many other films that take place underwater, this one makes the mistake of having characters who can hear each other underwater despite not wearing earpieces and having their ears exposed to the water.
Factual error: Towards the end, Quinn injects herself with a syringe full of Morphine to try and kill herself. She's dead in seconds. This does not act nearly that fast. Especially from injecting it in her arm.
Factual error: The scene where Pluto gets burned takes place at the Santa Cruz Natural History Museum, directly east of the Beach Boardwalk. In order to drive to the boardwalk in the scene immediately afterward, the Wilsons would have to pass through the line of Tethers holding hands.
Factual error: When Zapan speaks while his face is chopped off, the producers have failed to take into account the importance of mouth and tongue in producing speech. As a cyborg, Zapan could use speakers to produce a voice, but he isn't.
Factual error: She fires the entire magazine of a Glock into the alligator's mouth. When it is empty, rather than the slide locking back and the trigger freezing, there is an audible click every time she pulls the trigger. This could not happen.
Factual error: A fire is raging in a hardware store. The sprinklers come on. After the fire is out, the sprinklers shut off. Without anybody shutting them off. That's not the way automatic sprinklers work. Once the fusible link melts, they are on continuously until manually shut off at the valve, usually outside of the building. (01:35:20)
Factual error: Before the scene in the stable begins, John is pushed into the building by a series of cars cornering and ramming him. The order is given by two men speaking in Italian, but it's Italian with all the wrong cadence showing the words are not understood, and a pronunciation so bad words are barely recognizable - and wrong, like "Diteglie." (00:24:20)
Factual error: After they get the key from the game, the lock they open is a modern Kwikset Smart Key cylinder.
Factual error: Mohegan Sun casino is in the state of Connecticut. Connecticut does not have legalized sports betting and did not have it in 2012, when the film is set, therefore Julia would not have been able to place Howard's bet.
Factual error: It's a hard winter everywhere is film except in the scenes that take place in Denver. In one scene when Coxman kidnaps Viking's son, there are full leaves on trees and cherry blossoms. Moments prior there's a frozen tundra shot coming into Denver.
Factual error: The Sheriff of the small town is wearing Sergeant stripes on her shoulder sleeves. If she was a Sheriff then no chevrons should be on her sleeves.