Checkerboard pattern on images rendered over network

[TGS808]

I'm getting some strange artifacts recently when rendering over a network. So far it's only shown up on four images (all the same image but different angles). In the comparison below you'll see that the one on the left has a tiled "checkerboard" pattern in the blue area but the one on the right (which was not rendered over the network but on my single machine in the background) does not have it. To me the pattern almost looks like the break up of the sections rendered by the individual machines on the network. From image to image (for example, two renderings of the same right facing angle) the pattern is not consistent. It's on both but it moves around. Any idea why this might have happened?

Mac OSX 10.12.3
KeyShot 7.3.37
Render Queue 7.3.37