I have a theory that the earths core runs at a different speed than the outer crust because of a meteor hit.
I can’t figure out any reason why the core would spin at a different rate.
So, if the crust moves at a different speed, then it may swing pack and forth like a garden gate door on springy hinges. It goes back and forth until the motion eventually dies out.
That would explain the magnetic poles reversing too. Along with occasional extinctions.
Love your visualization of the speed of core rotation, versus crust rotation, and how those two forces interplay. Science is advanced by such thinking and ‘what ifs’.