I experienced the same thing. When I had killed the first three flesh golems and ran around in the sanitarium, all guards and patients were still there, alive, as well as the flesh golems. I was also attacked by wights when I entered the large room.
The second time, without the bug, all guards were dead and there were no patients left, only hostiles. I never ran into the wights that time. I had no problems killing Azo the second time either.
I have tried playing it the same way as the first time when I experienced the bug, but I haven't been able to reproduce it. It just triggered the first time I played through.