Hi 10 Dual Boot Display gets dark sporadically in Landscape Position

I have demounted Android from my Hi 10 CW1515 running only Win10 new installation and have installed all drivers again correctly from the support download page. Everything works fine again, but display from time to time gets dark in landscape position. When I turn to portrait, display recovers, but might disappear at once when turning back to landscape.
This happened already before I deinstalled Andoid- in the original installation, but only in the windows environment. Running Android display was stable- therefore I suppose it is not hardware related.
Can someone give a hint, why this is?