Hmmm. I found a setting that affects this, by going back a few years and opening a scene using AO. The AO Max distance defaults to 6. (I presume 6 inches but I'm not sure if Poser Display Unit affects this - anyway my PDU is inches so be aware.) I opened up an old Poser Pro 2012 scene where I was using AO and I found I had the AO Max Distance set to 90. In that scene, it rendered just fine without the crevice artifact. Of course the shadowed areas are much bigger but so be it.

AO Max Distance 6

AO Max Distance 90

So if you feel you really have to use AO, there appears to be a way to make it work.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)