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: The creep tells us that this is the first issue, but mere seconds after the famous ending of Father's Day we see fan mail on the second page, impossible for the first issue. (00:21:05)
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.