Some parts of SCS mesh is darker

[Soundwave2142]

I have noticed daf 105 have some dark spots, so I've imported it into blender, and discovered that looks like some faces are darker and it doesn't depend on the material, any SCS shader preset has this effect, but without SCS presets mesh doesn't have this effect. I've been wondering how to achieve same effect. Can't find anything on this on the internet.

Example, created new material on mesh just dif.spec with repeating uv, no AO ofc.

[Dotec]

it's vertex colors

[Soundwave2142]

it's vertex colors

Simple answer I was looking for, thank you.