There is an issue where the AI gets caught in a loop, or gets stuck idling. Sometimes this happens because a task he is trying to do is missing a resource. Occasionally this is not the problem and the issue is with the game's AI system, unfortunately not something I can fix. I think having only one human exacerbates or causes the problem. Sometimes the character breaks free when he gets too tired or thirsty for example, but if it takes too long it can be game ending. I recommend restarting the scenario if you run into this issue.