Vertical monitor resolution

I was playing around with a vertical monitor and it seems that eve recognises the correct vertical resolution in “Fullscreen” display mode, but when changed to “Fixed Window” cannot display the same resolution. (Using a 4K monitor) in fullscreen it can display vertical using 2160x3840 but in fixed window it’s either 1440x2560 (which is blurry due to half the resolution) or 5080x2560 which disappears off the screen.

Vertical 4k monitor in fixed window:

The only NVIDIA settings I have is the monitor rotated 90 degrees.

Any suggestions?

*cough Display settings > Windows scaling *cough :facepalm: