Tire casings have the structural part, the casing cords usually in a ribbon/strip like form before molding, and the rubber part. The rubber will conform to whatever shape it's being "told" to adopt by the casing cords. When the strips of casing threads gets deformed the rubber follows suit too. casing cords can break, shift, be poorly positioned when molded. These situations are fairly common and, to a degree, present in every tire (when new and having passed the manufacture's QC test these are so minor few notice) and can develop over time and use. Do replace the tire ASAP as if the casing cords are breaking the tire could fail during riding, the resulting change of control might not go over so well Andy