This has only started happening recently, on one of my maps, and it's incredibly annoying. I want to test one of my maps with bots and, no matter whether I do a nav_generate or a nav_generate_incremental, the game gets to "Calculating mesh visibility" (after having sampled walkable space) and then completely crashes back to Windows. I've tried enabling/disabling areaportals for the compile, there are no leaks and generation works absolutely fine on all other maps, including previous iterations of the one I'm trying to nav. I'm stuck on what to do. If anyone wanted to look at the BSP/VMF then I could upload them. Many thanks.