After selecting a Dropdown with the mouse, the dropdown can be activated and deactivated with the space bar

I want the Dropdown to only be activated by the mouse. I put all the navigation options on the dropdown to None. The dropdown can still be pressed with the spacebar after it has been clicked by the mouse.

I have read the documentation, Watched tutorials, looked at the Dropdown Script and TMPDropdown script, and tried different versions of Unity. Nothing works.