The evolution of some of the orbital elements of TIC 403792414 over the current century. Left panel: The variations of the observable arguments of periastrons of the inner and the outer orbits (ω_in – red; ω_out – blue, respectively). As one can see nicely, the major axis of the inner ellipse librates around the direction of the rotating major axis of the outer orbit. Right panel: The cyclic variations of the inner eccentricity (red) and the difference of the inner and outer arguments of pericentres (blue). See the text for further details.