I'll throw in another, "me too" to keep this going. Started with one companion but came and went and seemed to fix itself.
Then, once I got to the blighted village, it seemed to make the party as 2x2. They would be chained together as 4, but they seemed to only work in 2's. If I made the party stealth, only two would go into stealth. If I moved the party as a whole, only two would move.
But only a little bit after that (less than 20 minutes), it became that no companion would follow anyone else no matter the grouping or grouping order. Same with stealth. Nothing but reloading from a previous save has helped.
I personally didn't see any specific connections to when or why this started, but I do split and use stealth a lot, and from what I see, that seems to be the common thing for most people.
