■■■■ took some time to figure out exactly how to do this, but thank you! I had the same problem and had to change complexity to simple. I have no idea which mesh it was, but I just started selecting huge chunks of all of my static meshes and converting them to simple. Didnt take long (about 300/1000) and it was suddenly fixed. I dont know how or why this happened, but im guessing it was due to some kind of recent update or patch/ new version of Unreal being released.