Nanite setting produces weird black markings / splotches on geo

Hello…

I’m trying to follow a tutorial on environment creation, and converted some imported geo (from Quixel) into nanite objects. When I did, the interactivity did show improvement, but the objects converted (large rock formations) became mottled with black splotches, almost like bad faces or shadows.

Any ideas?

Running Windows 10, Ryzen 5900X3D (I believe that’s the CPU model), 64GB RAM, and an RTX 3080.

Thanks!