Strange lag (bounce into air, trees poor quality)

I’m getting a strange sense of lag/rubber-banding when moving over hilly/rough terrain, you get like, jolted slightly into the air…

Forgot to mention as well that, I’m finding that trees aren’t loading properly, they’re 2D and look very poor quality. As well as that in some areas, you are just stopped from walking, as if there is an invisible rock in your way for example.

Anyone else had this, and possibly know a fix?