Exceptionally annoying issue regarding fullscreen mode

[Soothsayer]

Recently (after the Fall Windows update), I've been having problems going fullscreen while in-game -- either with alt+enter or by simply clicking "fullscreen mode" in the options window. I've had zero issues prior to this update.

Basically, I'm having a weird issue where my screen "stretches" vertically whenever I enter fullscreen, which causes my cursor to lose calibration and lowers the game resolution (and cuts off the ends of my screen, to boot; for example, the input boxes in my chat windows are cut off, since I have my chat windows almost flush with my screen borders).

I have my fullscreen resolution set to 1920x1080, which is my monitor's native resolution. Strangely enough, going into "video modes" and clicking "accept" fixes the aforementioned cursor / border / resolution issues. I never have to select my resolution or anything. I just click "accept" and that's it. The trouble is, I have to do this every single time I tab out!

The alternative is to constantly play in windowed mode, but that presents its own issues, like annoying stuttering and my Windows toolbar, which obscures part of the screen and makes it impossible to read part of my chat windows.

Does anyone know what might be causing these sudden, annoying issues with going fullscreen?