I?m sure that it?s due to an excess of entities in the area. I had that problem when each and one of the banisters were breakable... individually.
Maybe you?re running in software mode or facing too much too enemies at time?. I learned from that bug, anyway ;). The bsps are on the way, please, be patient, by the time I released that beta I was working on them but I wanted to show you a little of it :).
Thanks a lot Ministeve. Any problem with dark areas?.