Tire Bubble problems of the 2012 Hyundai Accent

Tl- the contact owns a 2012 Hyundai Accent equipped with kumho ecsta asx tires, size 195-50-r16. The contact stated that while driving 40 mph over a railroad track, the front passenger's side tire failed. The vehicle was towed to the dealer for inspection where it was determined that the front passenger's side tire failed due to bubbles exhibited on the inside wall. The tire was replaced however, the replacement tire also failed while the contact was driving 50 mph. The replacement tire, which was also a kumho tire of the same size, failed due to tread separation. The tires were replaced. The manufacturer was not made aware of the failure. The dot number was not available. The tire failure mileage was 18,000. The vehicle failure mileage was 4,000 and the current mileage was 22,000. Kmj.