Continuity mistake: When King Arthur is fighting the Black Knight, there is a fire behind the Black Knight that is lit in some shots and nearly out in others. (00:15:55)
Continuity mistake: Near the end, Sam Clayton is nearing the finish. The audio leads you to believe that the horse is breathing VERY hard, but when the camera shows the horse, the nostrils are NOT flared as they would be on a horse that has been run to exhaustion (or even down the block). Also, the people filming this scene obviously have no clue about the nature of sweating in horses. They showed "lather" all through the horse's mane. The ONLY places horses will lather while sweating is where something is rubbing, i.e. underneath the saddle, the bridle or breast collar, where the reins rub on the neck or between their back legs.
Continuity mistake: During the chase sequence towards the end of the film, Roger's glasses keep disappearing and re-appearing between shots.
Continuity mistake: When the gun is telekinetically pointed at Deranian and his henchmen, Jason and the kids use this to escape and drive past both men. In the next shot, when the gun is seen still suspended in mid-air, the camper is seen right behind it.
Continuity mistake: When Molly dismounts her horse near the end of the movie the blanket slides off. A second later the blanket appears back on the horse.
Continuity mistake: In the scene after the first real battle of two tribes, the winning chieftain is about to chop off the heads of his enemies and is stopped by Sean Connery and Michael Caine. The chief threatens to lop off the head of the Connery character and is hit across the hand with the arrow he is carrying. The arrow breaks and pieces can be seen to fly off. In the next shot of Sean Connery the arrow is back in one piece.