Are you using a projector?
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No, the screen is a Sony KD75XD9405. In the center of the HDMI line is a Bose Lifestyle 535 Series II, but even without it, the issue exists.
It looks a bit like the Intel graphics issue of Kernel 4.4 which is part of a lot reports for other linux distros.
I've checked the specifications of OE6, kernel 4.1 was used (which is causing no issues in my case). LE7+ and OE7 are using kernel 4.4. IMHO there is really a chance to find the reason for this kind of issue in the built in kernel driver für the Intel Graphics.