Just what it says. I duplicated the follow package that Barbas uses and changed the conditions for my quest stages and edited the radius so he's not constantly sticking his nose up your rear. But he simply refuses to go through any door. It's not a navmesh issue, I re-finalized my cells. Once outside I moved him to me with the console and tried a few vanilla locations, still won't teleport. He fast travels fine. Could there be something I missed? The package conditions are met as he follows me when he's with me, except through doors. later in my quest, I set his follow package to Joto, and he follows him fine, but same thing, he won't follow through doors.

This might be a completely dumb and unhelpful comment, but I didn't think creatures could go through load doors.

Or, if they can, maybe put him in the potential followers faction?

Check in the Race window (General Data tab) to see if the "Can't Open Doors" flag is checked.

Found it! There's a Dog Race and a Dog COMPANION Race. The latter fixed it. Jubus, I would have never thought that this simple little quest to give a dog to Joto would have been this involved. I'm in at least 8 hours on this alone, mostly cursing and pulling my hair out. I need a beer!