@Poklop maybe try new HDMI cables, HDMI v2.0 or better, and see if problem persists. And try a different source e.g. Bluray player to ensure the problem is not with TV settings. I state the obvious, because sometimes the solution is hiding in plain sight.
Been there, tried that:) As mentioned earlier,7.x branch works fine
You Must Provide Logs Or you May Be Ignored. Link #1
It is known problem, not a bug report, logs won't help I guess.