The VMF Exporter did not output accurate rotation for textures on world brushes before WWMT 1.867. This usually occurs on faces that are nor rectangular. I'm working with Andrew Penry (who has helped a lot already to get the VMF texture exporting) to work this out once and for all.

Fixed: This problem was fixed for world brushes in WWMT 1.867. In that release, displacements were rotated incorrectly... but WWMT 1.868 fixed that too.