It's you. You contracted with someone to make them a product. Maybe you can go sue your subcontractors for providing bad components if you think you've got a case, but unless your contract specifies otherwise it's your fault if you use faulty components and deliver a faulty product.

If I make roller skates and I use a bearing that results in the wheels falling off at speed and someone gets hurt, they don't sue the ball bearing manufacturer. They sue me.