When you ignore politics:

YOU’RE absolutely correct, ENJOY.

Have you verified the specs on OPs headphones?

Maybe I missed it but I don’t see where OP said this happened while connected to a phone.

High resistance in a wire inside the sheath would generate more heat at that point, causing the plastic sheath to melt/bubble. So if the wire inside the sheath got damaged, pinched or some of the strands of wire were broken.