Continuity mistake: When Cornelia leaves some food and a can of soda out for Joe, the label says "Coke." In the next shot, when Joe goes to get the meal, the label on the can is "Coca-Cola."
Revealing mistake: When Jesse is cleaning out his room, he puts a tape into his tape player, and presses a button down on the top of it. But halfway though the scene of him packing his things away, you can clearly see the button is no longer pressed down, yet the tape still plays. (00:18:10 - 00:19:00)
Other mistake: Just after Isabeau falls from the abbey tower and turns into Ladyhawke, a soldier emerges onto the roof of the tower and questions Phillipe. An arrow is then fired (by Navarre) into the left-side of the soldier. However, he initially grabs at his right-side. After a couple of seconds he correctly grabs at his left-side, before falling off the tower. (01:00:26)
Revealing mistake: When Lowry first arrives at Buttle's flat to return the cheque, he hears a cough and turns to see a man smoking a cigarette, half hidden by a column. When he blows a cloud of smoke it is easy to see that it comes from a tube next to his mouth. He isn't even exhaling at the time.