So I'm playing the base game with the expansion, and I've made the room up to royal standards for the Stellarch to join so I can complete the final quest. Whenever I accept the quest, however, the Stellarch comes down (without the guards) as a visitor (blue name), meaning he just walks out the map, making the quest impossible to finish. I even made a second throne room, since the quest text leaves it ambiguous if you need one or not for him to join, still having the same problem. Anyone have any idea why or how to fix it?

It's worth adding that I have about 20 people in my colony (most of them are temporary, from quests), not sure if that affects it, but there you go.

https://imgur.com/a/5HJIaF7

EDIT: I took the empire traitor quest, but then patched the relations with the empire. Is that what causes it?