Robert W Hodson-KitchenAid-1760470669

I bought a KitchenAid double wall oven for almost $4,000. In 3 1/2 years, I've had 6 failures during the clean cycle that cost almost $2,000 to repair. KitchenAid says the unit is out of warranty, and they will not make good on their quality statement. How do I escalate and hopefully have the defective design or defective unit replaced?