I've been working on this map for a while with no problems like this. I was switching between adding more content and play testing, I get an error like this "Error: brush plane with no normal" and then a crash. It happens every time I open my own map (the giant works fine), with the mod tools, play testing or actually editing it with radiant. Meaning, I can't even edit anything in my map anymore. Although I can play the map inside Black Ops 3(actually going into steam and selecting "Black Ops 3" from my games list), just not with the mod tools. I tried using a backup I made an hour before, I tried verifying with Steam and I was actually missing 16 files, but hasn't helped me access my map.
Anyone know what I can do? I really want to get this update out because I'm getting more people playing this map than ever and want it to be a certain quality, which I don't think it is at right now.