Mine also has this problem - I just hanged up with Bose customer support. There was a known manufacturing defect, and an amount of these headphones are affected. I gave them the serial number, they confirmed, that although the headphone is outside of the warranty period, since it belongs to the defective ones, they replace it with a new one at no cost. I will get a shipping label, and in 10 days, a new headphones with 1 year warranty. I needed not to present original packaging or proof of purchase.