Same here. I just submitted a couple of bug reports. I can't even fight Cazador has my companions won't follow me into the final chamber and Cazador pops in as I get closer but doesn't monologue and I can't interact with him. Given the AI issues on following me, it feels like a memory leak.
I'm having the same issue. I'll do Astarion's quest and everything is fine up until I walk through the doors to the fight area. The triggers are broken, I can walk right up to Cazador and nothing happens, I can't interact with him either. I can't save or load game, just quit. Like he said, my companions don't follow me to the fight area, and I can't swap with them, if I click the potraits it will just move the camera to look at them, but I'm still in control of my previous character. This is my 5th playthrough now and it is the first time I'm having an issue like this. I am using mods, but they are the same ones I have been using since my 3rd playthrough.
