you could do the long old job of having two radiants open and copy pasting it over piece by piece into a new map, testing along the way

otherwise, your just gonna need to look around some more

I had this once from a huge brush

another time, i had grabbed on of the skybox brushes by mistake and mangled it up while working on something else

could be a bunch of things

you could do the long old job of having two radiants open and copy pasting it over piece by piece into a new map, testing along the way

otherwise, your just gonna need to look around some more

I had this once from a huge brush

another time, i had grabbed on of the skybox brushes by mistake and mangled it up while working on something else

could be a bunch of things

I happened to find an old version of my map file (really outdated lol) but if it works ill just salvage stuff from old map to new. Ill get back when compile done and edit this

EDIT:

I love you harry. Without your idea that there was a corrupted brush i would have never tried that... Many many thanks to your help, now i just gotta re do lighting and some stuff but most of it can be copied. Thanks to everyone else who suggested ideas also 

glad it worked out for you