Bypass the dealers and call up TMC directly and say you aren't satisfied with your dealer's solution. Might not hurt to also PM @
Moto-P who would probably relay it to the chief engineer who gladly takes action on issues like these since this car is his baby.
I used to work at a Toyota plant and seen them scrap completely built cars (Corollas) because they catch defects like these near the end of assembly line. They'd do a root cause analysis, fix the issue, queue up a new chassis, and build from scratch to replace it (or replace a bad batch).