For future people googling a fix for this bug, in my case it was a very well hidden enemy that stalled completion. Hope this helps! Join the group of operatives waiting at Spireton’s waypoint. Then walk towards Spireton, but instead of entering the main gates, turn left and circle the property that way. At one point you’ll run into a hole in the wall where you can enter the Spireton area. There was a single enemy still there for me, chilling against the side of a building. After I killed him, the group of operatives finally burst into action and I got the “Spireton is finally ours” conversation.