Deliberate mistake: The doctor appears to write just three numbers or a short wavy line on the back of his business card for the phone number he told Marjorie to call (to get a second opinion about Nathan). (00:42:35)
Factual error: Sassoon's Military Cross medal is shown ending up thrown in the Mersey and sinking. In his own words from "Memoirs of an Infantry Officer", published in 1930 - "I ripped the MC ribbon off my tunic and threw it into the mouth of the Mersey. Weighted with significance though this action was, it would have felt more conclusive had the ribbons been heavier. As it was, the poor little thing fell weakly on the water and floated away as though aware of its own futility."
Revealing mistake: During one of the chase scenes, an SUV hits a rock barrier and flips over landing on its top. The car spins around, and we see that it is empty. The driver then climbs out as if he was just in the vehicle.
Factual error: The initial police scene takes pace 20 years ago. The present year is 2021, so 20 years prior would've made it 2001. The police Chevrolet Tahoe at the opening scene of the film was only made from 2007 and up. (00:05:40)
Factual error: Charlie gives Kaz a flare gun to shoot a shark in the mouth underwater. She manages to fire it underwater and the flare travels several meters. It is impossible for a flare gun to activate underwater. And if the flare was fired into the water it will only travel one or two feet. (01:13:00 - 01:18:00)
Visible crew/equipment: When the group realise they have triggered the alarm system, one of them says "Shhh listen" and the boom microphone appears briefly above his head. (00:45:26)
Continuity mistake: When Tom knocks down the bike at the car, the position of the fallen clothes changes between shots.
Continuity mistake: When Sharyn backed up to her bed after looking out her door, the top sheet was re-arranged differently from when she got out of bed. (00:05:25 - 00:05:53)
Factual error: There was a lot of thunder and lightning before the lightning strike that set the barn on fire, but there was no obvious loud thunder AFTER the strike. Lightning can be seen BEFORE the sound of thunder (because lightning travels faster than sound). (00:03:25)
Factual error: Morse code is supposedly being transmitted by the blinking street lights. They supposedly spell "For 3veryth5h1ng that 7iv3s is holy." I know Morse code. It was just a random scattering of letters. (01:00:05)
Revealing mistake: The possessed "Helen" that Fr Daniel threw to the ground by grabbing the back of her hair landed like a stuffed doll, not person. The "body" was mostly padding and the fake "Helen" kind of bounced or teetered after hitting the ground. Also, her arms stayed hidden in front of her whereas a real person would be stretching out or moving arms to try to land as safely as possible. (00:21:35)
Revealing mistake: The Giles brother who got "hung" when he fell after getting shot by MacMasters can be seen moving his body (mostly arms). (00:04:06)
Revealing mistake: There was already a gap in the snow mounds (which looked like a snow sledding path with no fresh tracks) when the "kid" was sledding down the steep hill. (00:02:40)
Factual error: The movie largely takes place in California during the 1990s. California's mandatory seat belt law went into effect 1/01/86. When Mickey was driving Kyd to the cemetery, they were not wearing seat belts. Also, Kyd was 8 years old at the time. Although legally permitted to ride in the front, it is advised that kids sit in the back seat for safety. Considering Lyla was recently killed when a driver ran a stop sign, Mickey should have been more concerned for Kyd's safety as a passenger. (01:12:58 - 01:15:05)
Continuity mistake: The dead rabbit was thrown onto its left side with its back almost parallel to the table's edge (width) and its nose/head almost in the corner. There was a bowl of several brown eggs several inches away from the rabbit's stomach. When the camera shifts, the rabbit's head has shifted at an angle away from the corner, its rear feet are slightly hanging over the table's edge (length), the bowl of eggs is touching the rabbit's stomach, and the eggs are piled on the opposite side of the bowl. (00:05:35)
Continuity mistake: As Batman is walking through Arkham, he passes the Riddler's cell. Riddler leans up against the glass of his door with his hands against the glass near his face and mouth. When the angle changes to behind Riddler, suddenly his hands and arms are down more to chest level with his right hand outstretched towards the side of the door. (00:07:02)
Revealing mistake: The "movie set" steps were so steep they almost looked like they were flat against the wall and the handrail posts were so close together they looked more like vertical blinds. The little dog was able to scale the steps one-by-one, but the larger dog had to leap with effort to get to the top. Also, the baseboards on perpendicular walls (lower right-hand corner of the screen) were not in alignment (off by at least 1"). (01:11:54)
Continuity mistake: When two officers go to inform Ronald Whitlock (Bruce Willis) about his sons, Ronald shoots his pistol at the Black officer and hits him near his inner right eyebrow. (A large black spot can be seen between his eyebrows.) When the camera shows the dead officer, the black mark is gone and the bullet hole is on his forehead centered about 2" above his left eye. (00:06:40)
Factual error: During the escape from the farmers market a red London bus is in the background. Those busses aren't used in Gloucester.
Audio problem: During Rusty's conversation with Hardy (about knowing he doesn't want to be at the orphanage), some camera views of Hardy from behind show his cheek (and therefore his mouth) making little and insufficient movement for the words he is saying. In particular, Hardy saying, "Look, you can make me play this little game of yours" and "We done here yet, coach?" didn't show adequate facial movement from a rear angled view. (00:22:30)