Other mistake: When the captain comes face-to-face with the Thing for the first time, the upper right frame becomes blurred once the door starts opening until it closes followed by a scene change. Very odd except maybe they were trying to hide the minicharges to create the bullet holes after they close the door. The implanted charges are very visible when the scene is not blurred. Also there is a small charge in the wooden frame of the door near the door handle. (00:57:32)
Other mistake: Lock Martin is not wearing his Gort glove on his right hand in the first frame of him carrying Patrica Neal.