While escorting Dritten for the first time I got disconnected. After taking him again from the barracks when he got attacked on crystal coast he got stuck. So I went barracks again and used another route, through west city gate and down the safe beach path to Roshaven. Next stage he got attacked by pale dragonflies and the same thing happened. By being stuck I mean him standing in one place, periodically vanishing and reappearing and taking no damage from monsters if he is under attack, with all hits being evaded, similar to monsters that go back to their area after chasing player too far.
Update: I used "dismiss" on him and could proceed alone to the druid grove. After reading sign he reappeared and everything was ok to the end, though on the way back to barracks I was very cautious to avoid aggressive monsters and managed to do it without attracting even single one.