Have you seen the gear? Pretty weird looking...
...also flexible, not rigid. Not an off-the-shelf part at all!
My driver's seat rear height adjustment has the same failure...was quoted $350 at the dealer for a new motor assembly.
Broken shaft caused one side to raise and lower only, leaving the entire seat listing to one side.
So for now, I adjusted until it sits level then disconnected the harness from the module under the seat until I can find a suitable replacement...