Ok I was testing my map and at a certain part it shows "Trace backed up past 0.0" and then it shows "Master Heartbeat timeout 0.055616 against 400.000000" or some other number like that in there.
And that null brush effect pops up once i go past a certain point and then i go a little further and its back to normal. And I didnt even use null textures in this part. All my brushes are valid and I have no leaks.