I think it's because the wrong grass texture is loading (it loaded springwood for me)? Try Theme Mixer -> Terrain -> Grass Texture. Playing with the slider fixes it at certain altitudes, but not all (that I could make work). I've swapped to the SCT-HOMECOMING one, but I'm not sure it's the right one, but it looks OK.

I have the same issue, let me know if you get a fix