Logged out of game with Thrall attached to follow. This was to solve a movement lock where I could not move left/right. I immediately logged back in, and the thrall (Freya) was wandering around the house, up and down stairs… I was finally able to grab her with the MOVE command and relocated her out of doors , where she stopped roaming. When I tried to get her to follow again, the game gives me the Too Many Following error message. I tried logging out and back in, but didn’t have any luck yet… I suspect a server boot may solve the issue.
Found this while testing solution for the same problem; so sorry for a late reply to this issue. If you let your character sit for a bit and go into afk mode (where the camera spins around you) it seems to reset the thralls and will allow you to make them re-follow you without the server reboot.