Meh. I thought this problem was solved with P8, but not.

I fought Poser Pro for months because whenever my character had a closed mouth, she ended up with a long black line all along her mouth opening is I used raytraced shadows. Horrible.

My first renders with P8, I didn't pick up on it, because I had the mouth just slightly open. But the problem is still here. See attached image. Keep in mind that the settings for the image below were very high.

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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