I have the same problem with the top race scene (if i tried too often) and the
Aerial Car Kit (if i had modified it a little bit).
I thought it was only my pc but now i am relieved ^^
Its just the same Texture. maybe you should mirror every second foresttexture. then it looks more like a wood then 100 textures side by side.
and a tipp for realism trees grown even on mountains straight up.
its a little bit boring if you want to drive the hole track and there are places you canīt drive over, even with the numpad speed