I purchased a pre-reg Mazda MX-5 2.0-litre from a dealership with 170 miles on it in the summer of 2017. The handling got progressively worse and I took it back to the dealership for investigation a few days before the six month anniversary of its purchase (its mileage was now 3300). Investigation has shown the rear differential has failed and it has been replaced under warranty. A separate issue of a rusting rear brake disk was also dealt with under warranty (both disks skimmed) and assumed to be linked to the failed differential. However the handling issues remain, albeit slightly reduced, and a comparison drive with an identical vehicle from the dealer showed that there is still something wrong with the car. The vehicle remains at the dealership for ongoing investigations. What can I do if the dealership is unable to fix the problem to my satisfaction? Do I have to allow them three attempts to resolve the problem before instituting a rejection process? My concern is that the differential failure is not the source of the handling problem but a symptom of another material fault with the car and given that it is a sports car these early significant problems give me concern.