Corrected entry: How does Alex suddenly know that the werewolf cornered by the police was David? For all everyone else knew, it was just a giant, bloodthirsty mad dog. Not to mention, throughout the movie until that point, she didn't even believe in David's ramblings about being a werewolf.
Corrected entry: When David turns into a werewolf for the first time and starts killing people, his fangs and mouth are covered in blood. When he wakes up in the zoo, he doesn't have any blood on his lips or hands or any part of his body, and he certainly should have tasted blood in his mouth.
Correction: David has turned back to human form, so his body has gone through a major transformation. There is no reason for there to be any blood left on his teeth or a bad taste in his mouth just like there is no trace of him being a werewolf. After all he is left dazed and confused by the experience.
Corrected entry: There is no explanation why David transferred to a hospital in London even though the attack took place in Yorkshire.
Correction: Granted there is no explanation in the movie but it's not a mistake. People get transferred between hospitals all the time. It's to be expected that a hospital in London has better facilities and as an American citizen (in a coma), the embassy may have requested that he be transferred to a location near them.
Correction: The people in East Proctor purposely moved David far away from their village after his attack because they knew he would become a werewolf. They just managed to kill off the first one and so didn't want another.
Corrected entry: In the bar, Jack refers to the pentagram on the wall as a pen-ta-gon.
Correction: Character mistake - Jack mixes up the two words, or he is simply unfamiliar enough with geometry that he only remembers the word "pentagon" for a shape with five corners.
Correction: He is saying "Pentangle." Which is a pentagram.
Correction: That's kind of the point. She finally believes him and puts 2 and 2 together.