I set the ‘Cursor’ option as ‘None’ on the text, the button, and the widget.
All the elements of the widget then. 
Could you test if this would work here; in the widget:
Buttons are notoriously finicky to work with. What you’ve described and shown should not be happening if the Player Controller does, indeed, hide the cursor.
there is more complex interactive logic
Is there any other script / actor / widget in your project manipulating / effecting hardware cursor and its visibility?