Somone said they used wd-40 contact electric spray on it and that solved it, others say you keep pressing and unpressimg the mute button, if you still have warranty contact manufacturer.
If you're a tinkerer you can disassemble the headset and clean the mute button from the inside, if that doesn't solve it then I would put a small solder point on its tip from the inside and keep it unmuted all the time and not play with it, maybe use software matting instead after.