V-Sync divided screen (on some Intel Graphics only?)

Hi all,

thanks for your incredible work!
Here is a problem I encountered: On one of my machines (see below), I got V-Sync working after some trials by using wglSwapIntervalEXT(1); Framerate is around 60 then, unpredictable tearing is gone.
BUT I still have a strange effect: First 30px (approx) seen from above lag (move a little bit slower), the Rest of the screen is good. So each movement brings a "divided screen" at always the exact same height. Something like a tearing, but always on the same line. This happens with different screens exactly the same.

With two screen connected (mulitply mode) first monitor is as described above, second monitor shows a clearly divided tear also, but the border on this one is wandering slowly downwards. With second screen in extended desktop mode all tearing is gone.

I only encounter this on one machine: Intel Core i37100 @2,4GHz. Graphics is HD Graphics 620, Windows 10. Compiling machine is Windows 7 , OF is 0.9.3 vs. Difficult to do a lot of testing, as this is happening at work. But I'll try my best if necessary...

thanks a lot!
oe

No source file or test is identified. Start by reproducing the divided-screen tearing on the reported Intel HD Graphics 620 and Windows 10 setup, focusing on the wglSwapIntervalEXT(1) entry point and the single-monitor and multi-monitor modes described. Done means identifying a reproducible cause or a confirmed fix, with a regression test if the behavior can be tested.