Also, there's a glitch where floor isn't made of floor, meaning entire sections of the floor lose function as floor, causing oxygen leaks. They still appear to be made of floor, so it's hard to find the exact source of sudden suffocation. Once again, awesome game!
Firstly, I noticed the raids too, it may just be a bug with spawning because of the newest entity, the trader (just a thought).
Secondly, I've had the floor do that to me too. Just refresh and load back into the world, that normally works for me when it happens.