Other mistake: In all the shots of ET wearing the white sheet the two eye holes are about a foot apart, so he could see out of the holes properly, but when Michael finds the white sheet ET had been wearing he lifts the material and we see that the two eye holes are only about two inches apart, which makes no sense. (It was Gertie's sheet that had eye holes so close together).
Other mistake: On board the USS Reliant as it orbits Ceti Alpha 6 the systems panels show ship diagnostic diagrams including a wire model of a Constitution class hull, something the Reliant doesn't have. (00:13:01)
Other mistake: The shape of the crystal shard is all wrong. In a flashback scene a urSkek is seen "shattering" the original, pure crystal by hitting it with a rod on one of the crystal's flat surfaces. For argument's sake we will say that in their universe it would be possible for this to create a spear-shaped hole in the crystal. However, the top of the shard is a rounded surface; it should have a flat, slanted top to match the top of the hole it came out of. Could pieces have broken off the top of the shard to give it the rounded shape? If that were true the final solution would not have worked; only the whole, pure crystal would restore the urSkeks.
Other mistake: When Conan gathers flowers to "take to the girl", the flowers that he is holding as he mounts his camel, are very long-stemmed, and dark purple in color. In the next scene he is riding the camel and the flowers he is holding are not only very changing color as another post indicated, but they are also very fake plastic / fabric flowers. In the same scene, Conan is then seen wearing a strong of flowers around his neck, those too are very fake flowers. (01:05:00)
Other mistake: In the Ring Game, Flynn throws a shot that Crom catches and returns. When the shot hits Flynn's rings, it takes out the third and fourth ring. Problem is that any other time, the impact only takes out the ring that it hit. Close inspection shows a solid hit on the fourth ring only. The only explanation is that since Flynn continues and jumps the "gap" in the rings, this was a deliberate set up to bring the end to this sequence and move the movie forward.
Other mistake: When the hunter throws his cross-x at the witch's backside, the witch screams a second before it even makes a strike sound. And when he goes to pull the cross-x out in the far shot, there is nothing in her back.
Other mistake: When the thresher blows for the second time, Mr. Ages slides down it into a large chamber into a basket. When he falls into it, he is translucent for a second.