Hello everybody , im just here to ask about BSP Geometry , When I use to work with BSP tool I mean Extrude, split triangulate and things like that engine is just crashing after 20 sec , I can’t work more than 20 sec with BSP Brush ! I have 4.3 through ! -_-’ I Am only one who used a lot BSP BruSH ?
I have same problem. BSP brushs are slow, they take 1 sec every time i move a simple cube. This is so annoying. UNDO doesnt work with bsp because it freezes editor about 30 sec and then crash.
I just find my self today , start a new project and choice “empty level” I used to take by default but looks like there is too much things on default one and it’s too much buggy , I hope that’s can help you and remember choice " empty level" 
Hey ReDFragg3r,
BSP system can really bog down editor, especially as you use more of them in same level. On slower systems, this can lead to crashing. This is a known issue, and we hope to address a lot of that with Geometry 2.0 tools. There isn’t a timeline for that right now, unfortunately, but you can vote for it on our Roadmap to show developers you’re interested in it:
In meantime, best thing you can do is to go to Edit > Editor Settings > Level Editor > Miscellaneous and disable Update BSP Automatically. This should let you work with brushes with less overhead, and then go to Build > Build Geometry when you want to update it all at once.
Hope that helps!