Bonsoir Pilou:
agree with Michael...you can't expect fillet engine do something in a tight wrinkled area like that
but you can refine this object using sweep like this way



you can see after sweeping you have anymore wrinkles in that sharp area



i attached file,check inside the browser i marked splines i used
last orange one is final result.
your original shape without wrinkles,filleted using blend G2,mataining enough sharpness corner in front area
hope it helps: Mauro :)