Nearly most main-stream geophysicists agree that the main problem regarding polar shifts is that none of the theories can explain how the angular momemtum of the earth can be overcome to account for sudden polar shift.
The best that geophysics can demonstrate is the earth's nutation cycle every 41,000 yrs for a minor declination axis of 1 to 2.5 degrees of arc. If this were to occur in a tight 1 to 200 yr. period ( remember 1 degree is equal to about 69 miles of earth curviture ) that would in itself induce , enormous magmitic disturbances, & crustal volcanic eruptions, earthquakes , weather changes ,at weak interface areas. The after-effects alone might last 1000 yrs+ until the equatorial bulge had re-adjusted itself. All this from a mere 70 to 200mile+ axis shift due to nothing more than the natural gyro-mechanical movements of the earth.Yet, here comes the smoking gun;
These calculations are all mostly based on astro-physics which do not take into account the earth's second orbit which allows for the nutation cycle as compensation for loss of orbital synchronization of both orbits. They can not complete both orbits simultaneously so to compensate the earth undergoes both precession & nutation at different cyclic speeds.
What 2nd Orbit? If you think I mean the 90,000yr longer orbit, that would be incorrect ( Such an orbit does exist as proven by Milankovitch ).The Milankovitch Theory (a theory of climate change) didn't take into account variations in earth's angle of inclination in relation to the sun's equator.Most planets have a little variation of between 1-5 degrees from the line of the sun's equator as they circle the sun. Milankovitch took into account those variations ( & the famous Jupiter Effect Cycle ) from the other planets because their variation is more than 1 degree+ ,and therefore observable.
If you check your astronomy atlas you'll see that the earth's variation is always listed as 0 degrees.That's because any lower variation is not readily observable for the earth by telescopic observation.Since what can be observed never registers at more than 1 degree it is officially assigned as zero degrees. This still allows for the possibility of .00 to .85+ degree of variation which means the earth's true motion around the sun is a helixical path the compromised result of the regular circular orbit plus a 2nd Minor Orbit,perpendicular to the regular.
When you think about it, if the outer planets can exert a gravitational pull while they themselves vary from the solar ecliptic the earth must be ever so slightly yanked outward,yes to be sure, but also slightly downwards or upwards as well. Clearly logic dictates that even if it is at zero degreesof variation presently, it cannot maintain this forever. IT MUST VARY AT SOME POINT.
That variation is your 2nd orbit!This isn't observable because it is superimposed upon the first ( regular orbit at .00 degrees variation ). Still, per the circumference of the earth's orbit about the sun, the diameter of this orbit can vary from 2 to 3 million miles, and is what provides for cycles of axial stability.The greater the diameter of this orbit,the faster the precession cycle the more erratic the nutation cycle as the axis shifts to compensate assisted , by its own equatorial bulge. I do not take credit for this theory, but I can't remember where I heard it from.