[camelreef]

Wherever you want it Sherlock :-) you can also do it via ssh: DISPLAY=:0 xrandr --output whatever --mode 1920x1080

 Sir, yes, Sir! :o)

So, same conditions/PPAs/kernel as above, still intel driver.
Adjust Refreshrate disabled
I issued the 1080p xrandr command through ssh after the movie started playing, as Kodi got going with an initial switch to 2160p.

Yes, artefacts showed-up, very visibly, 15mn into the movie.

Debug log: http://paste.ubuntu.com/26216448/