Normal Mapping Issue
-Textures that do not have a normal map on them - are having a "emulated" normal map applied which causes very bad visuals.
-Just simply have a model that doesn't have (name)_norm texture with it.
-Explained in detail by Seven here:
LH: "considering the optional emulated normalmaps are off by default unless you play with -tenebrae, -game tenebrae, or r_shadow_bumpscale_basetexture > 0"
So if you are getting this error, ensure none of these 3 options/settings are active.