Golden Halla - Ithiren Disappears

I've noticed pop-in a few times with creatures during a fight, but right now in the Dalish camp in the Exalted Plains I've been having troubles with Ithiren and the Keeper disappearing.

The Keeper will toggle between popping in and out while you're standing right next to him, but at least it's consistent.  You know he'll appear again shortly.  But Ithiren is gone and hasn't reappeared.  The Halla quest is completed, and the notification system keeps hassling me, but there's nobody home.

Anyway, does anybody have a workaround, or a way to encourage a missing NPC to reappear?  I've left the area and returned on foot, and tried fast traveling, but nothing has worked.