That the entire earth can tilt in space is a confusing point to humans in understanding pole shifts. Humans are drenched in Newtonian theory, which explains the
planets maintained in their orbits based on centrifugal force and momentum. All of this falls apart when Newton's math is applied to your Moon, so very close at
hand yet too large and slow moving to even stay up there, per Newton. Nevertheless, Newton is force-fed to humans in school so they contemplate pole shifts in
this venue, and boggle. Per Newton, both the Earth and another passing planet would plod on, just passing but not affecting each other except for gravity, a tug in
this or that direction.
But this is wrong, on several points.
Human's measure their magnetic field on the surface of the crust, which is composed of hardened lava which points in the direction of the magnetic field at the time the lava hardened, and thus sends many signals to dilute any given compass measurement. The crust moved, after lava hardened, and this is a buffer for the true magnetic field coming from the core. This is far stronger, and reaches further into space, than most humans imagine. As we have explained, magnetism is a particle flow, as is gravity. Additionally, rotation is not caused by some initial momentum long ago instituted but by the various components of a liquid core in motion, attracted and repulsed by this or that in the surrounding solar system and thus trying to get closer or farther away, within the confines of the sphere the core finds itself in. But without arguing these points, the issue in pole shifts is what the weakest link is when the magnetic fields clash.
Is it the orbit position, which might tilt to allow a pole shift to occur simply due to orbit changes? Perturbations in the orbit, due to gravity pull, but not a tilted orbit, per human astrophysics. Would a passing planet draw another closer to it, temporarily? This argument would not cause a pole shift, but a temporary slowing down or speeding up in the orbit path, per human astrophysics. It is drag, rotation slowing due to extra man-made lakes around the equator, that silly argument put forth by humans to explain a barely perceptible slowdown in rotation speed, lately increasing? Drag would cause a slowed rotation, but not a tilt. Humans, schooled into dead-think in their autocratic schools, have no way to explain pole shifts without being open minded and exploratory, those attribute that get them punished in their schools and yelled at by the Shepherds of the Sheep of the sci.astro Usenet. So mention of a pole shift, and its mechanisms, creates a yawn, not a query, in most.
Indeed, there are many factors that hold a body in its orbit, beyond what human astrophysicists conclude. But to avoid endless arguments about endless factors, let us simply state that the orbit involves many bodies and forces outside of the planet itself, and thus is not the weak link. The orbit continues on, and does not tilt. Gravity likewise would not cause the planet to tilt, but rather draw closer or, if one is given to consider the gravity counterpoint, the Repulsion Force, to push away and not tilt. Both we and humans agree on these points, but for different reasons. But what holds the core of the Earth so firmly that it cannot move in its molten mush, during the passage of another planet with a magnetic field? This can move, without affecting the orbit or the relative position to other bodies re gravity factors, and it does move. Place two magnets end to end, and they are happy to line up. Place two magnets side by side, and they both try to move so that they line up. Make one of these magnets several times the mass of the other, and the larger dominates in this motion. Thus, the Earth moves, in place, in its orbit, at the point where the passage itself occurs, the north pole of the passing planet no longer approaching the south pole of the Earth, but passing it, thus dragging this south pole along with its north pole during the passage.
Thus, you have wandering poles, magnetic fields pointing in all directions in frozen lava, crust shifting to bring mastodons into the polar circle with green grass in their stomachs, flash frozen to be discovered and pondered over by modern man. And thus, during this close approach of this very magnetic planet that is heading toward Earth from the south now, you have a swirling core heating the Earth up from the core upwards, causing polar and glacial melt which cannot be explained by any increase in atmospheric temperatures, and magnetic diffusion which is estimated by humans to eliminate the Earth's magnetic field in 1,250 years at the current rate. Of course, they are wrong in their estimate but at least are honest enough to acknowledge that diffusion is occurring. The approaching passage, and its effect on the Earth, explains these phenomena, where the Shepherds of the Sheep of sci.astro have no such explanation save the laughable.