Mouse not mapping to the screen resolution

In Windowed (Fullscreen) the mouse can only click on the top left 1/4th of the screen. It’s as if it thinks the resolution is 480x600 instead of the 1280 x 800 that the screen is set to.

For example, if I want to click on a menu button on the options menu in the centre of the screen, I need to put the mouse cursor up to almost the top left of the screen to select the button in the middle of the screen.

How can I get the mouse area to map to the set resolution?

Running on Mac 10.15 Catalina (15" MacBook Pro 2015)