I have my main village near Herndean and an "interception outpost" at the bridge between Farnworth and Brigand HQ. In the outpost there is only housing and a stockpile with food for the NPCs. The NPCs in the outpost are only fighters to intercept reclamation groups and set to worker when there is nothing to fight.
One of the NPCs doesn't eat nor collect food when hungry and then goes wandering over the whole map (I assume he tries to get to the main village to get food there). I caught him now several times in the middle of nowhere and brought him back to the outpost. I double checked that there is enough food in the storage and that the NPC is assigned to the outpost, which both is true.