Can't clear controller binding to first input gamecube

[alterlego]

Hello,
I want to use three controllers: two bluetooth gamepad + one overlay control (touchscreen).
However one physical controller keeps controlling player 1 which should only be controlled by the overlay.
I "cleared" the first gamecube input and then cleared every single binding. Yet it's stuck like when I set up controller 1 to be emulated by a physical gamepad. "Clearing" seems thus broken.