I have my Win10 taskbar on the top of the screen and whenever I go full-screen Firefox moves it's window down so low that it cuts off the bottom ~15% of the win

I have my Win10 taskbar on the top of the screen and whenever I go full-screen Firefox moves it's window down so low that it cuts off the bottom ~15% of the window and I have to drag the top back up to the taskbar to force a resize in the bounds of the screen. Sometimes it happens to other windows (never Explorer) but Firefox is consistent.