Presentation #202.07 in the session Dynamics Beyond Neptune.
Self-gravitational, axisymmetric disks of eccentric orbits in near-Keplerian potentials are unstable to an out-of-plane buckling. This spontaneous symmetry breaking appears in Kepler elements as an increase in inclination, a decrease in eccentricity, and a clustering in argument of periapsis. Later, the broken symmetry seeps into the plane of the disk creating a lopsided m = 1 mode seen as clustering in longitude of periapsis. We discuss the possibility that this instability occurred in the primordial planetesimal population in the early Solar System thus explaining the peculiarities in orbits of the eTNOs and Sednoids.