Notice this first with imported Daz hair that has overlapping Textures with Opacity maps (existed in previous iC7 builds as well.)
The more opacity-mapped textures involved, the heavier the rendered artifacting will be.
ie - if one, no artifacts, if > 3, becomes increasingly noticeable.



EXAMPLE:
Daz OOT Samira Hair - imported from 3DXchange, has 9 separate hair-piece textures, each one has an opacity map:


(A) Veiwport size effect on rendered artifacts (See images beginning with '1080p')

-Viewport Size Normal (Default)
renders at 1080p - some artifacts

-Viewport Size Full Screen (Ctrl-7)
renders at 1080p - more artifacts and missing texture

-Viewport Size Mini (Drag up timeline so viewport is shrunk to less than 1/4 of screen height)
renders at 1080p - minimal artifacts


(B) Rendered Resolution Size effect on rendered artifacts (See images beginning with 'VPNormal')

-Viewport Size Normal
renders at 1080p - some artifacts

-Viewport Size Normal
renders at 2160p UHD - more artifacts and missing texture

-Viewport Size Normal
renders at 600p - minimal artifacts


(C) Super Sampling Amount on rendered artifacts (See images beginning with 'FinalRender')

-Viewport Size Normal @1080p
Final render at 0x SS - some artifacts

-Viewport Size Normal @1080p
Final render at 2x SS - more artifacts and some missing texture

-Viewport Size Normal @1080p
Final render at 3x SS - more artifacts and more missing texture


ADDITIONAL:
*Note 1 - Preview render is also susceptible to the phenomenon and does not avoid issue.
**Note 2 - format of render - JPG, BMP, PNG, TGA - has no effect. All susceptible to the phenomenon.


Thanks for providing the opportunity to improve iClone product and the experience of the iClone user community.