To explain, my partner is just getting into the quest line and is just nearing the War Within quest. Following that, can we complete quest lines together at the same time? When I tried to replay one of them with him, the quest point didn't advance with his.

Edit: When we were playing the quest point together, his advanced and mine did not. Is it just because it's a rerun? Or do you have to run every mission twice?

Edit 2: My partner runs on PC, I run on Xbox. My partner is usually host. We will start quest lines together (in my case I will replay a completed quest line as my active quest) and play through the first mission. After completing the mission in the objective, my mission does not progress. My partners does. Perhaps it's a rerun bug? We have not tried it with any of my new quests that he has access to yet because we're getting him caught up with the story line.