As Dave pointed out, the problem is not consistent with black borders but also with graphical glitch around windows, which I still think, has something to do with, how shadows are rendered.
Adding an alternate attachment/image for graphic glitch.
As Dave pointed out, the problem is not consistent with black borders but also with graphical glitch around windows, which I still think, has something to do with, how shadows are rendered.
Adding an alternate attachment/image for graphic glitch.