Tire Bubble problems of the 2002 Ford Ranger

Tl - the contact owns a 2002 Ford Ranger equipped with goodyear wrangler radial (p) tires, size p235/75r15. The contact stated that while driving approximately 50 mph, the vehicle began to shake. The contact pulled over to the shoulder of the road and noticed that all four tires had bubbles on the sidewalls. The vehicle was taken to a local repair shop where the tires were replaced with another set of the same tires. The contact mentioned that a week later the failure recurred. The vehicle was taken to a dealer where it was advised that all four tires needed to be replaced. The vehicle was not repaired. The approximate failure mileage was 44,000 and the current mileage was 50,000. Kmj.