I keep getting "face normal is incompatible" on both xnurbs (the one shown and the empty area above). At first I thought it was inverted normals, but I fixed that for all surfaces using this material and reverse, then restarted the editor, but it still won't create an xnurbs above G0. What could be the issue here? Is the area just too complex?

I am at video 3.2 and I noticed that the top surface I created is not perfectly symmetrical. I think it may have been caused by moving control points accidently without having both sides selected. Is there a way to fix that by mirroring without it creating a seam? The surface has no seams until I mirror, so the second screenshot shows the result after mirroring, but I would like to remove that asymetry