[mackmgg]

I had the same thing happen to my Pros, with one being much louder than the other and the noise cancelling barely working, and it turns out they just needed cleaning. A couple years of gunk and dust getting in the vents and speaker grill and one of them was noticeably worse than the other. After cleaning it turns out both were quite degraded and are now much better with fully functioning noise cancellation. Worth a try if they're otherwise good and you want to keep using them.