Continuity mistake: When they finally arrive at the bottom of the sewer, Eddie's bandage is on a different cheek. (01:59:00)
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.
Continuity mistake: When the Losers Club is in the sewers, the bandage on Eddie's face is on the wrong side in one shot.
Continuity mistake: After they find the club house Beverly tells Ben how handy he is. A bang of her hair is falling on her forehead. In the immediate next wide angle the forehead is clean.
Continuity mistake: Mike's bandage is on the right arm instead of the left (and as previously mentioned, in the same scene, Eddie's bandage is on the right cheek instead of the left). (01:59:59)
Continuity mistake: When the Losers are in the Library, after killing Bowers. They call Bill who is at the funfair. It is night and dark at the funfair, but at the library, daylight can be seen through the window.
Continuity mistake: The mug in the antique shop keeps turning around between shots. Check the painted symbol on it.
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.
BaconIsMyBFF
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.
BaconIsMyBFF
And Pennywise would have been asleep in 1992~1993 so that whole scene after the arcade makes no sense.