This is a small buglet still present as of Beta 2-18. If you research the Fortified Civilian Ship Upgrade to give your trade and refinery ships more hull hitpoints, a small oddity happens. Instead of going from say 500/500 to 600/600, you only get 500/600.

Now the AI thinks these ships have been damaged and needs repair. The Robots Crusiers will chase these ships all over the map trying to 'repair' them up to full health. The ship do not stop at a repair dock to repair themselves either. A simple code fix would be after the upgrade research, make sure the ships are at the new full ship hull strength.