I built you shelter. Clean water and food, decked you out in armor and weapons, a http://images.akamai.steamusercontent.com/ugc/367406736571924360/C0CAC21B38F27E8597029DD7F5EEE02C6E1246AE/. And yet at the castle settlement, none of them attend their post that I have given them. I've seen em occasionally standing by them, so it's not an accessibility issue. They seem to like to walk around on the walls and such. Why do guards not stay at their stations at the castle?

Or anywhere else for that matter. Mine wander between guard towers or lounge around all the time at all my settlements. On the plus side, at least they shoot at things during an attack. Of course, so do my scavengers and farmers so...

One thing that I have noticed is that if you assign a settler to a Guard Post, he isn't locked to that Guard Post. He splits his time between as many Guard Posts as are present. To be sure that ALL of your Guard Posts are manned, you need to have as many settlers assigned to Guard Posts as there are Guard Posts. (Usually, I can't afford to have that many settlers doing guard duty. Too much farming and trading needs to be done.)

Going in between posts is fine, problem is they are caught standing in places where no guard posts are at all or even in a path to one. The are not en-route, just standing on certain spots ontop of the wall.Maybe the castle has "natural" guard posts on it, where the AI is told to go patrol even if there are player made post available.

The other thing about ALL settler assignments is that they pointedly do NOT remain at their posts 24/7. More like half the day on, half the day off. And when they are NOT on duty, you often find them just standing around, or else catching up on sleep.

They tend to stand around at 6-11pm (in that ball park). It's a 'break time before bed' kind of behavior that they have. If you put down a bar/restaurant the settlers will congregate around the bar and find seating if any is available.

At some settlements i have found that if you build a guard post, (or market stall for that matter), within the boundaries but near the border of some parts of the allowable build space, the settlers won't service them.

For those few occasions the solution has been to progressively relocate the improvement away from the build space boundary until the settler populates it.

A settler is capable of producing up to 6 defense. In practice, this means three guard towers. So if you have more than one guard tower, then the one guy will be shuffling between all of them.