I'm doing the Daedric quest, A Daedra's Best Friend. I've followed Barbas directly along from Falkreath, and we're now just outside Helgen. He keeps wandering into Helgen, then turning around and wandering back out again, as though he's forgotten where he's going.
I've never known an AI to get lost before, and I checked - sure enough, the wiki confirms this as a known bug:
Some times Barbas may have trouble when travelling through Helgen. He may proceed into Helgen, wander around and walk back out repeatedly.
However, it doesn't offer any suggestions on how to remedy this. Is there a fix for this problem? I'm on the PC so can use console commands as a last resort. I have not discovered Haemar's Shame with this character so can't fast travel there.