What REALLY puzzles me though is this:
If I play "standard" M4V/MOV encoded video files or even DVD images from a (Raspberry Pi 3) server through DLNA, the graphical issues are ALL over the place. However, if I play the SAME files locally on my Macbook Pro with LAN and uPnP turned off, everything is running smooth with no graphical artifacts/tearing or any sign of GUI going nuts.
Is this ye olde "macrovision" story for a new generation, or just a coincidence? I've tried to debug quite extensively for the last hour or so, and it seems somehow related to streaming/network activity.
(By the way, I can't figure out a way to post URL's with a proper link.)
Andreas