random brush - where is it?

[EmNudge]

so I have this brush sticking out in front of blue spawn.

and it's possible to just walk through it and sometimes get stuck in it. Problem is that I have no idea where it's coming from and, although identical, red spawn doesn't have this. Here is the hammer view of this:

 

[Freyja]

This is probably caused by an invalid solid trying to fix itself on compile. Double check and possibly remake nearby brushes.