I saw of graph of the precession cycle once and it appeared to occasionally skip a
beat — perhaps when eccentricity got near zero — this makes some intuitive
sense at least... (cause of Obliquity cycle is less obvious than precession of axis; perhaps some contribution comes from the Earth - Moon orbit and Earth + Moon — Sun orbit not being in the same plane — although the Moon's orbit will «average» near the plane of the Earth - Sun orbit
over a relatively short time, but there's lunar orbit eccentricity, etc,... residuals might build
up...?