Other mistake: While laying the pipeline toward the ocean, the pipe is being joined so that the female end flows into the male end. The male end should flow into the female end.
Other mistake: During the battle in the cavern, the (almost) bald Indian Warrior helping Ghost is stabbed by a Viking and dies in Ghost's hands. When Ghost kills the Viking and continues on, you can see the Indian Warrior still breathing. (Timecode refers to the European Extended Edition). (01:01:55 - 01:02:55)