Why can't Minecraft go full screen properly?

Whenever I open Minecraft I have been having the issue where the game opens but it is only displayed in the upper left corner, despite it being in full screen. Anybody know how to fix this issue?

Notes: Running Windows 10, using the proper graphics card for the program, correct resolution selected in launcher, have tried current and previous Minecraft versions, using an external monitor attached to a computer, have tried duplicating monitors, extending and 2nd monitor only.

Any help greatly appreciated.

Oddly enough the problem seems to have fixed itself. I has already tried restarting my computer before to fix it, but for some reason today when I tried restarting again it fixed it.

1.Try pressing Alt+Enter multiple times till it changes to full screen. 2.If this doesn't work press f11 once then press the maximise button (present near the close button. Just like any other window) and press f11 again. These should work.