I'm relatively new to Civ V. One of the most annoying elements so far is the need to refresh worker orders at the end of every turn. Seems to happen if they are near the borders. They will complete the job if they are escorted but this is often unnecessary. What I can only think must be a bug is the case where they are no where near a border. After recently destroying the Mongols and now being the only Civ on the continent, the workers will still require refreshed orders every turn. They are well within the interior of my territory. And on top of that, if I give a worker orders in my original territory (territory that was always mine), the worker will complete they order without an escort or need to refresh. I suppose the workers could be afraid of the old Mongol ghosts that haunt their former territory.