OK, so as far as I figured the whole AI render is wrapped around face detection.
If it did not detect a face, it does not render. I mean it does, but it comes out jagged, blurred, distorted, smudged or all of the above.
iClone render of a basic scene:
Same rendered with AI. Settings do not matter at all, it would come up pretty much as this:
Now I added a tiny face of Camila at the corner and everything falls in place:
I hope it fixed at some point…