My fullscreen is unusual

whenever i press "Toggle Fullscreen" or press F11, my game screen gets all weird. About 50% of my screen (In the upper-left area) shows only a fraction of my game. I cannot see my hotbar or the ground. only numbers of items and durability bars appear. the rest of my screen is black, or if I've recently pressed escape, a bit of the pause screen is there instead of the blackness. My mouse will still go into the black/pause area, but clicking does nothing. This only happens in fullscreen mode. I have tried triggering a debug manual crash. it crashed but fixed nothing.

What I expected to happen was...:
a regular fullscreen gaming session

What actually happened was...:
A very annoying bug

Steps to Reproduce:
Im not sure if that's possible. Sorry.