It sounds to me like the car buyer has no claim against the body shop, just the breach of warranty claim against the car company. The car company has to live with whatever the body shop did wrong or wasn't able to fix properly; the car company might possibly have a claim against the body shop, but that would be based on the contract between them. If I were the attorney for the car company, I might think about bringing that claim into the buyer's lawsuit, in what's called a third party complaint.