This is my third time and I'm familiar with altitude weirdness having lived in Denver for several years, that rollercoaster effect.

The other parts of the descent were smooth until specifically hitting its maximum bank, then it suddenly got squirrelly and then stopped as the plane began to flatten. It's as if the degree of bank was beyond the plane's limits.

I've flown hundreds of times and can't recall ever experiencing something quite like this.

EDIT: I just realized my original comment was written incorrectly. The plane didn't expectedly bank, it's that this started happening at the top of a hard bank.