I have the same issues even though my rig can run this game at 120fps on lowest settings no party effects. There are a lot of large explosions and smoke effects in o11 which almost all my static members saw massive fps dips for a few seconds when it does atomic ray (and maybe mustard bomb too). Always had this issue in ultima when the comets come down and explode, which also cause a lot of smoke effects, so I'm assuming that's the issue with that particular floor (o11). Not sure about the other floors, can't remember.