Second mission of the campeign mode, half way in. I don't know what triggered it but my two main ship producing colonies stopped making ships. Yes, there are starports, and they all have factories. They all approve of me too so I don't see why the workers would just stop working. On the game map, it says in the little window that there are zero weeks left before ship completion. So, I finish my turn and still it says that there are 0 weeks left. I don't have many ships, so maintenance isn't a problem. I don't know what triggered it either.
