Hrymr: So the objective is to defeat all other corsairs (so three in total) and then sail to the Darwin principality.

In my case they have died while fighting each other, "X corsair has died" has triggered for all of them and the initial message has a check mark, which wasn't there before, but nothing else happens, and sailing to Darwin does not end the mission.

So I am wondering what are the win conditions there? Maybe the player has to defeat at least one of the enemy corsairs in battle? Or it's a bug and it should have trigger and move the quest to the next part?

AfricanWishbone: The objective doesn’t state that you have to kill the corsairs yourself, there is a mismatch in the town names, Darwin in the objective and darwin are n game, not sure if that makes a difference. Each objective seems connected to one to create an armada for each faction. Sailing to Darwin should end the mission though, sorry the objective are difficult to read