Seems like if coherent mode is set to 0.25-0.3 or more it will create a two faced looking characters. In the image attached you can see a line between the left and right sides of the character. We are rendering at 3000 samples and this should be more than enough if we use coherent mode
By te way version 2.x never did this with coherent mode enabled.
Seems like version 3 splits image into 4 parts when rendering