Grid views do not match up with program in 4k resolution, scaling does not work

[Mapsking]

I am trying to set up GTK Radiant for use with an OA Gamepack, but everytime I load up the editor (1.6.6, just downloaded fresh), the program puts the viewports in a tiny window, and crashes regularly. It seems to be related to using 3840x2160 resolution on Windows 10, but I am not sure. Here is what it looks like.

If I try Windows High DPI scaling, I get something like this:

Either way, anytime I do anything, like try to move the viewport sizes, it crashes on me, and I can't do anything, or even try to use it.

[webketje]

Potential temp fix:

Set screen resolution to Full HD (1920x1080), work with GTK Radiant, then revert.
This should already at least tell you whether it's only the resolution or there's more at play.
I suppose the File > Properties > Compat settings will be of no help