Please, see attachments for additional info and screen shots with artifacts.
Also I've tried the latest git drivers from here:

https://launchpad.net/~oibaf/+archive/ubuntu/graphics-drivers?field.series_filter=xenial

with the same results:

libdrm: 2.4.68+git1606070630.70b640
mesa: 12.1~git1606090730.037ce5
xserver-xorg-video-nouveau: 1:1.0.12+git1606020733.1da8a9