Hi, I think that i have found a bug for TeamViewer 14 latest version when your running it in Windows 10 1809.
It's regarding the scaling, if you have different scaling on your displays when your running dual displays the graphic / scaling bug are there, but if your running both displays on the same scaling setting for example 100% and 100% then the bug are gone.
I have tried it in different devices and different displays and also changing the cables its always the same issue/bug. I have tried revert back to Windows 10 1803 and there I don't have the bug.
I'm not sure if this issue are because of Windows, TeamViewer or Intel's drivers but the issue are there for me in two devices and because of that I can role out hardware issues but both devices do have Intel graphics so.