Character mistake: When Polly answers the phone and is told of the log drifting in the channel, she immediately yells to Sean and tells him this. However, she does not leave enough time for the caller to be able to tell her all this, she leaves 1-2 seconds before passing it on to Sean.
Character mistake: After Ricky has just killed his girlfriend with the car antenna, he's challenged by a police officer. Officers would never walk right up to someone who have just committed a murder. Police would always order the suspect into a position that presents the least amount of threat and minimal chance of resistance. Grabbing the officer's gun would never had been an option.
Character mistake: When Modoc is suggesting what type of blood to drink, he suggests pigs blood B-. Swine don't have B blood. They have A and O blood only.
Character mistake: When Mac describes what he saw after Blaine was killed, he states that he "capped off 200 rounds with the minigun." At the rate the minigun fires, and the length of time Mac was shooting, he fired at least 10 times that amount. Perhaps he meant to say "capped off 2000 rounds." This adds to another mistake: the ammo pack Blaine carried only holds 500 rounds but much more than that is fired during the course of the film.
Suggested correction: He actually says "capped off 20 rounds, in the minigun...full pack" just the word spacing is a bit odd. 20 rounds refers to his normal gun which ran out of ammo quickly.
Character mistake: The little girl asks Kristen "what's your name?" Kristen replies "Kirsten". (00:05:59)
Suggested correction: I hear her say "Kristen." The transcript and subtitle even say "Kristen."
Character mistake: It doesn't occur to our heroes (admittedly kids) that you don't need to understand German at all in order to read it out loud. It's arguably easier to read than English! The only inscrutable letter would be "ẞ" but Scary German Guy's right there for help. (True, this is essentially what they end up doing in the end, but they still come about it through a "you don't need to be of age to be a virgin" realization rather than the even simpler "you don't need to know German.").