Disassemble and Diagnose the Stopper

What happens here

Remove the malfunctioning 'lift and turn' tub stopper from the drain. Upon inspection, it becomes clear that the brass threaded post of the stopper has an unthreaded gap between the top and bottom threaded sections. This gap prevents the stopper from fully engaging with the drain's internal threads, causing it to spin freely instead of securely tightening or loosening. This design flaw is present in both the old, problematic stopper and a brand-new replacement, indicating it's a widespread manufacturing issue rather than wear and tear.

Goal: Understand the cause of the tub stopper's malfunction