Funny thing is I saw someting like this,(just not quite, mine were multicoloured squares) in my first serious P7 render. BUT they all disappeared once the render was 100% done. And they didn't save onto the final render. I was "LIKE WTF?!" when I saw thenm but they disappeared.

It MAY have to do with the viewport being obstructed during the render but I'm not sure. In my case they didn't actually apear on the saved render...

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.