गूफ़

When Mark leaves Charlie to his fate in the ductwork he is shown crawling toward the camera with no sign of the bag of weapons collected earlier. After reaching the remaining survivors, he kicks out the vent cover and enters the room feet first. There is no bag of weapons and he goes immediately to hug Shelley. At no point is any bag shown from the time Mark leaves Charlie until Mark hugs Shelley. The very next scene is Mark going through the bag of weapons showing the group what he found.

At around 56 min, when Charlie and Mark are crawling head first through the narrow ducts, they are somehow able to turn themselves around to kick out the grating with their feet first.

When the electrician is found savagely attacked by the monster his cigarette can be seen hanging out his mouth the wrong way.

(at around 39 mins) When Charlie is talking to Nikki in the storage room, the head of a third person is clearly visible, but all the characters are accounted for and are elsewhere.