I usually use it as a mesh library for the 3D Gridmap, and I set only the snow textures to triplanar, not the wall texture. You also need to tweak the triplanar parameters a bit.
In any case, I'm not really sure what error you're running into. If you could share more details, that would be great. By any chance, check if the material in Godot has any transparency enabled, and if so, disable it.
