This typically happens as a result of a process known as fusible separation. After washing and pressing a garment, the shell fabric—the outside layer of clothing—and the interfacing—the glue used to keep it in place—can separate because of poor fusing or slight shrinkage.
The suit jacket is the most typical attire for this. The shell fabric must be correctly fused, and that is the responsibility of the manufacturer. Bring it back with the original receipt if you see this on your jacket or any other item of clothing, and we’ll try our best to make it look fantastic once again.