Noticed in the course of the in-game keybind rework. In-game: Settings -> Control -> Keybind Preset to "Custom"
Clicking the "Use gridmenu" toggle has a visual lag; and does not update the settings toggle (however it does update the actual interface on every other click). So instead of acting as a 2 way toggle, its acting as a 4 way toggle and adding legion unit errors or map shaders is enabled into the console on alternating clicks.