I started this 2V2 single player game where i teamed up with an AI. After i took both the enemy factions(they surrendered), I chose to continue playing. At this stage my AI ally declared war and i went on to crush em. However I now have conquered all the planets and this enemy faction does not exist on the map anymore. Oddly enough this faction still manages to put a pirate bounty on my head. I manage to out bid them and this pirate fleet always just hand around the edge of the pirate base(since this faction does not have any planets anymore). Now i have also destroyed the pireates but my game never ends since this last faction continues to exist in the diplomacy screen.