Character mistake: This ship's computer, 'mother', says "declention" instead of "declination" when giving coordinates of the planet.
Character mistake: Namibia was said to be in West Africa. Namibia is in Southern Africa.
Character mistake: In his opening prologue, Burt says the Graboids have been contained to the Northern Hemisphere, showing a map highlighting the Graboid attacks of the first film in Nevada and the second film in Mexico. However, it overlooks the Graboid/Shrieker attack in Argentina, in the Southern hemisphere, shown at the beginning of Tremors 3, an incursion Burt personally put down. It's not like it was classified - characters in that movie talk about it being reported by CNN, and characters in the Tremors TV series talk about it as well. And it's not like Tremors 3 is no longer canon, since Burt makes two references to being swallowed by the Graboid in that movie (which also becomes a plot point in Tremors 6).
Character mistake: When recruiting Burt to help repel the Graboid attack in the arctic, one of the team members says he's ideal for the job because of his experience hunting them on two continents, a reference to the first two films (Nevada and Mexico in North America) and Tremors 5 (Africa). However, this repeats the mistake in Tremors 5 in overlooking the Argentina incursion stopped by Burt at the beginning of Tremors 3, which gives him experience fighting Graboids/Shriekers/Ass-Blasters on three continents, not two. Burt, himself having overlooked Argentina in Tremors 5, does not correct her. And it's not as if the film is completely ignoring Tremors 3, since it shows the flashback of Burt being swallowed by a Graboid in that movie, which is how he got infected with the deadly parasite killing him here.
Character mistake: The professor identifies the "sea monsters" as plesiosaurs from the Pleistocene. Plesiosaurs became extinct at the end of the age of dinosaurs, nearly 60 million years before the Pleistocene. Of course, the Loch Ness Monster might be an exception.
Character mistake: A priest is holding a globe with a fire to light the globes carried by others. There are two lines with globes approaching the man with the lit globe. The first person in the line from the right has trouble lighting their globe. She starts to return for a second try, but apparently thinks better of it and continues on with the unlit globe.
Character mistake: At the start Smith takes a Krestal ballistic computer and barely holds it out to get wind speed. The proper technique is to hold it at arm's length into the wind.
Character mistake: The banner of the fundraiser event for the Gotham upper class says "Childrens Hospital", no apostrophe. (00:11:55)
Character mistake: Immediately after the crash, when Reeves is carrying his youngest child Sophie, the actress opens up her mouth, even though she has already drowned. (00:14:43)
Character mistake: Given how smart the lead is he doesn't seem to know the proper dosage of sleeping meds he put into his mother's coffee. He placed in enough to possibly cause an overdose.
Character mistake: There are signs out front as the Spenglers arrive at the dirt farm. One of the signs is a call back to a scene in Ghostbusters 1984. In the scene, Ray quotes the book of Revelation: "And I looked, and he opened the sixth seal, and lo, there was a great earthquake. And the sun turned black as sack cloth, and the moon turned blood." When Finn Wolfhard reads it he misquotes the line saying "The sun became as black as cloth."
Character mistake: Kathy Ireland as Wanda speaks mostly in a slightly squeaky voice. But in one scene she uses her own regular voice.
Character mistake: Whenever a YouTube livestream by jacksepticeye is shown, his name in the URL is misspelled as "jackspecticeye," and his username is spelled with a capital J when it should be a lowercase j. (00:30:16)
Character mistake: The telegram from Mount Wilson Observatory mentions "extraordinary electric waves." The Italian dub also makes up that it was sent from "Dr. Johnson," when it is in fact signed "William Johnes."
Character mistake: They keep calling the vehicle a milk truck but it says "ice cream" on it. (00:23:55)
Character mistake: The woman with the AK-47 doesn't have the covers on the red dot optic open. In other words, she can't see her target.
Character mistake: David Dastmalchian is the Polka-Dot Man, hyphenated in the comics, and in the end credits of the movie. Then again, when Waller threatens to kill everyone off, the name of the character appears in print as Polka Dot Man, no hyphen. (01:49:40)
Character mistake: When Dan takes the blue vials from the fridge, he is told to take all 12, but there are 15 vials.
Character mistake: When Joan is searching the web looking for information on what monkeys eat, there is a section on the screen that reads "The diet of monkeys varies form fruits, leaves." Obviously the correct word for this sentence should be "from" not "form." (00:36:21)
Character mistake: Towards the end of the movie when the Giganotosaurus is attacking the group and Claire gets the rope wrapped around her leg and pulled towards the dinosaur Owen actually shouts Bryce before saving her instead of Claire.