Had similar issues first with the left then the right. I believed it was the os update. Called support once and they kept me going w/ the same three or four questions and two reps for 1.5 hours. They then moved me to iPhone support and an actual call, I was chatting w/ the two reps. I was done and declined. Was going to just return them to BestBuy but were out of the return window. I assumed it would be extended a bit as it was a Christmas present, but was not. My wife, tired of hearing me complain, called Apple support and got them to replace both units. New units work excellent. Waiting for them to fail or update.
Original Christmas gift version worked great. Easily created a 'Good Seal' according to the Tip Fit Test. Then one day when I took my first phone call I heard the left ear "crackle". I described it to support as "clipping", a term often used in the stereo field do describe a failing or underpowered but over volumed speaker. Soon after, the right ear started and I could do it on command by merely speaking sharply. Then Siri became fickle. Not every time and I thought it was my hoodie on my jacket causing issues. I decided to attempt the Tip Fit Test and couldn't get either ear to create a "Good Seal" consistently. Like one in ten attempts and never both ears at the same time. I tried all the sizes again many times. All this was w/ NC or Transparency on. So, they became an overpriced version of the originals and very annoying in either active mode.
Glad my wife purchased AppleCare+ as I see sending these in often until they fix whatever is wrong with them. I did get me my replacements overnight. And they are phenomenal when working correctly.