I'm not sure what is triggering it, but I'm getting rooted in place in phase 2 of the Lambach fight. My character's movement animations are active, but it's like I'm surrounded by an invisible wall. Dodge roll does escape it occasionally, but rarely. It looks like it only happens when I'm close to the boss - right up to the north edge of the arena. I'm attacking using Bladestorm, so I might only be getting stuck there because I spend most of my time there. I read earlier that it might be triggered by the tentacle slams, but if it is it's inconsistent.