I tried without the Progressive Refinement with 20 samples and it looks crisp enough, and really fast - thank you!

Alright, so. To test, I applied my character's regular lip color, to avoid that change in glossiness, and deleted the Background material I had. Lo and behold:

The eyebrow bug is back! And the yellowed skin (look at the lips - they're very rosey pink in P11). Eyes looking sickeningly red! Ouch.

Eye shader:

I think I read somewhere that P12 uses lower numbers in scatter? If that's true, that must be what's happening to the eye there. But the yellowing in the rest of the skin is not just low numbers - that keeps happening in very low numbers unless I unplug the SeparateRGB+Scatter map from ScatterDist there, I've checked this a lot.

Also, that one streak of lighter hair on top of her hair? I suspect that's a hair card that has its normals pointing down, so it's rendering the backside differently. Shouldn't happen - this would break longer hair even if we make hair with all cards aligned. Buuut might be something something in the node noodle from that hair material, again, I don't know. Will play around with another attempt of hair shader just to test.

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Feel free to call me Ohki!

Poser Pro 11, Poser 12 and Poser 13, Windows 10, Superfly junkie. My units are milimeters.

Persephone (the computer): AMD Ryzen 9 5900x, RTX 3070 GPU, 96gb ram.