Character mistake: We see the lead driving on the motorway to get to the cottage. She leaves at junction 6 for Princes Risborough. Which means she is on the M40 that goes to Birmingham. When she arrives the host asks about the drive down and mentions the M4. This is a different road entirely, that goes to Swansea.
Character mistake: Mia's Sea-Monkey, in a vertical position, was shown sinking to the bottom the jar. It isn't clear if the Sea-Monkey was dead or if Mia was referring to it when she said, "She's gonna freeze to death, Aiden", but Mia should have known how to properly care for her Sea-Monkey (or refer to the instructions) and, realizing the room was too cold, should have done something - such as wrapped a towel/blanket around the jar and/or moved the jar to a warmer location (e.g, near the fireplace). (01:22:33)
Character mistake: The Predator is jumping through trees, then landing in a creek, splashing in the water. Its cloak barely flashes for a moment, then it can walk through the water still cloaked. This is a prequel to the other Predator movies, where it is already established that with their cloaking technology, even in the future, walking in water or getting wet disrupts the cloak and it malfunctions. (00:37:10)
Suggested correction: Even though Prey takes place 300 years before the original movie, its technology isn't necessarily "worse"; it's just different. In the 1987 film, the "Jungle Hunter" has a blue-tinted cloak that shorts out in the river. In Prey, the Feral Predator has a reddish/orange-tinted cloak. Fans suggest the red cloak might be an older, more robust (but perhaps less "clean" looking) version of the technology that wasn't yet sensitive to moisture but lacked the optical clarity of the later models.
While that is a plausible explanation, without concrete proof or a given explanation in the film or subsequent adjacent material, it still leaves it as an inconsistency in the movies. With all the other tech and weapons this predator has, being more primitive, and their species and culture taking any advantage they can in a hunt, it also doesn't make sense for them to use a cloak in the future with "more advanced tech" that is weak to water, when Earth is covered in water and it rains.
Character mistake: Nolan said, "Everybody knows that no sharks swim in freshwater" and Spencer said, "They don't come into freshwater", but there are freshwater sharks (e.g, river sharks) and bull sharks (not true freshwater sharks) can survive in saltwater or freshwater. Jacob Harper (National Aquarium) pointed out eyewitness accounts of sharks swimming up the Mississippi River and "bull sharks have kidneys that recycle salt" but did not mention the glands near their tails that help keep salt in their bodies. (00:08:08 - 00:29:50)
Character mistake: Aunt Monica wants to give a pendant to Rhoda that has a garnet in it. She says that it would need to be replaced by a turquoise, since that's Rhoda's birthstone. No month has turquoise as its birthstone. (00:06:04)
Character mistake: Doreen/Mom told Rose she'd be back from the store "in a jiffy." Rose asked, "How long is a 'jiffy'?" and Doreen replied "in about an hour." "Jiffy" typically means VERY fast (perhaps as short as a nanosecond) and, even if people have different perceptions of how much time a "jiffy" is, an hour is excessive by general standards and does not reflect its true meaning. (00:32:50)
Character mistake: Over the phone, Julie told her sister Sara, " I got them [parents] a bouquet", pronouncing the "T" in bouquet. Bouquet has French origin so the "T" is silent. Bouquet is properly pronounced like bow-kay (American English) or boo-kay (British English). (00:00:55)
Character mistake: Tyler said, "Charlie says you're [Ben] gonna tell your folks that you got that girl pregnant this weekend." "This weekend" is a misplaced modifier. Ben didn't get the girl pregnant this weekend; Ben is supposed to tell his folks this weekend that he got a girl pregnant. (00:22:15)
Character mistake: Reina asked Cory if they could "do that thing" because it was helpful for her medical school training. Reina then put a raw slab of steak/meat across his forehead and made slits in the meat as well as jabbed at it. A medical student studying to become a brain surgeon should know about and practice the safe handling of raw meat. (00:23:10)
Character mistake: Amber was a poster artist and Ben was a musician. Amber said to Serena, "You know a lot of people and can afford rent, so why do you want to live downtown?" The downtown area or center of a city is especially attractive to artists (as Amber should know) for its art/cultural/entertainment opportunities and experiences. Amber was also implying that it was more expensive to live in the suburbs than in a downtown apartment (where rent can be unaffordable to all but at least the upper-middle class). (00:07:20)
Character mistake: Marjorie's supervisor said the police found Nathan "torturing an animal [dog], there was a struggle and he assaulted one of them." Marjorie then asked, "Is he violent?" Her supervisor replied, "I have no reason to believe so. I mean, he did resist arrest, but that's probably out of fear" and the mental health team said there was "no obvious psychopathy." Social workers/mental health teams should have assessed cruelty to animals and resisting arrest as indicators of potential for violence. (00:03:55 - 00:04:30)
Character mistake: [Story 1: Hungry Joe] It isn't clear what blood test results the doctor receives for Joe, but Laura pleads that she "really needs to know what's wrong with her son" because "He eats, he eats, and he eats, and he never stops." The doctor dismisses Laura's concern and replies, "Growing boys eat... we'll see you in six months." The doctor should order additional tests. Blood tests can show "false negatives" and the appropriate blood tests may not have been ordered in the first place. (00:04:25 - 00:05:18)
Character mistake: The Captain of the USS Fragasso comes onto the bridge. A Petty Officer says, "Officer on deck," and salutes while looking out the forward windscreen. He should have said, "Captain on the bridge" and not saluted.
Character mistake: The crew deride Garrett's title of Flight Officer, claiming that she can't have it because she hasn't flown in combat. In fact, Flight Officer was a genuine WAAF rank corresponding to Flight Lieutenant. Many RAF officers holding the ranks of Flight Lieutenant, Flying Officer, and Pilot Officer were not aircrew, despite their titles.
Character mistake: The Georgetown University camera feed for "Faith" lists irrelevant personal info like "Mark Goodman - Baby Daddy" alongside "Biomedical Research," while showing "Threat Analysis - Unclear." If she's not flagged as a threat, why is she being tracked at all? And why is gossip-level relationship info in an intel overlay?