I'm in Act II, I have followed through with the Bloodmoon Island quest-line, and just finished the first round of exorcism with Jahan. When he asks if he can accompany me to Arx, I'm given two options - say yes and tell him to wait on the Lady Vengeace, or say no.

I've tried reloading multiple times, but the outcome is always the same. I say yes, he begins walking towards the Lady Vengeance. I get a quest update. I check the update, it says I've declined Jahan's offer for him to accompany me to Arx and that I'll be taking care of this demon on my own, despite me explicitly choosing the option for him to travel with me. I fast travel to the Lady Vengeance, Jahan is not there. I return to his home - Jahan is not there.

This is a serious issue in my opinion. It's not only breaking what I perceive as a core choice in the Lohse's plotline (no spoilers please), but in doing so it means I'm unable to exit the conversation without it having a lasting effect on my campaign.

Hopefully it's fixed very soon.