Never thought about resetting my prefs. That's a good idea.

But on your claim that's not an artifact, but a shadow.. sorry, I'm not buying. It's a shadow in the same way that the nasty blotches in other darkened places are shadows, sure. But if they are that bad of shadows at high Q settings, I'd call them artifacts. There is no way a shadow should be a solid line like that. Not on an organic surface like the lips. It looks very bad. I could draw in a shadow like that with a permanent marker. (And note, I have a shadow blur radius of close to 5 on both lights in the render I just posted.)

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Hardware: AMD Ryzen 9 3900X/MSI MAG570 Tomahawk X570/Zotac Geforce GTX 1650 Super 4GB/32GB OLOy RAM

Software: Windows 10 Professional/Poser Pro 11/Photoshop/Postworkshop 3