Worldcraft does not seem to save triangle (5 sided) brushes too well in the .MAP format. It's fine in the .RMF format. Here's what I did:
I created your standard 6 sided brush, selected and then turned on vertex manipulation. I moved one of the corners in 2D view so that it was linearly aligned with two others, thus creating a triangle (but with 4 vertices). Then I saved it as rmf. Then I saved it as .map. When I close and then re-open the rmf, the triangle is still there. But when I close and re-open the .map file, the triangle has reverted to its original square (cube) shape.
Is there a workaround for this?
Thanks,
DieparBaby