Revealing mistake: During Conan's sword-fight with one of the Queen's guard (after the escape from the castle), you can tell the sparks were added in afterwards. At one point, Conan's back is to the camera and the guard attacks from Conan's front and a spark is seen in front of the back of Conan's head when his head should have blocked the view of the spark.
Continuity mistake: During the ambush scene, when one of the baddies activates a trap and gets stabbed in his stomach, the position of his hand is inconsistent between shots.
Revealing mistake: When Conan's assistant Malak is climbing down the waterfall, he causes some rocks to fall, one large one obviously lands right on him, but he is fine in the next shot. (01:24:15)
Revealing mistake: Just after the fight between the tied woman versus the 6 men she jumps on a horse and starts going up the hill. At that moment the camera moves sideways while showing the back of people's heads, in a hat you can see the information label (make, studio etc.).
Revealing mistake: In both shots rowing toward the ice castle and back from it, the shot is obviously using some sort of rear projection, as the film running behind has marks such as hairs and scratches that have been amplified. The contrast between the main shot and the rear projection is different too.
Visible crew/equipment: During the opening fight before the queen reveals herself, the camera shadow, along with the shadows of a few crew members can be seen when one of the fighters is thrown to the ground. The camera pans down, and you see its shadow.