Other mistake: When Lawrence is looking at his wound in the mirror, it has slightly healed. Later, when Sir John visits Lawrence in the asylum, he shows the bite mark he got from the feral child to Lawrence. Since Sir John is also a werewolf, the bite mark should not be there.
Other mistake: Gwen regrets getting Lawrence involved, saying that if she had never sent him that letter, he would still be in New York. She sent Lawrence a letter when Ben went missing in the theatrical version but, in the extended cut she went to tell him in person instead. Yet the "letter" line is retained in both versions even though it doesn't make sense in the latter.
Continuity mistake: The chunks of ice in the asylum dunking scene appear and disappear. When Lawrence is brought to the surface, he has two chucks of ice on him that fall off leaving none, but when the shot cuts to him being raised and locked upright, there's a chunk of ice on his right arm. A minute later when he's lowered again into the tank, there's a large chuck by his hip but vanishes when the shot switches showing Lawrence's left side. (01:07:45)
Character mistake: Sir John describes St. Columbanus as a gypsy from the East, but in fact St. Columbanus was Irish and founded one of the first monasteries in Scotland (on Iona island), one of the most important in Christendom.
Factual error: Sir John claims to have removed the gunpowder from the silver bullet four bore cartridges. However, he had not removed the primers, thus there would not have been a mere click from the falling hammers but a most definite bang from the primers. Furthermore, in some calibers the pressure from the primers may actually be enough to propel the bullets even without gunpowder.
Continuity mistake: When Lawrence is going through his first transformation in the mausoleum, his hand is right next to a candle. In the next shot, he is near the door leading out off the mausoleum.
Factual error: The film is set in 1891 and shows London's Tower Bridge in operation. The bridge wasn't opened until 1894.
Visible crew/equipment: Near the end of the movie, before they turn into wolves, you can see the reflection of the crew in the window.