so I have a S9+ I got it about December of 2019 and its had this problem ever since I got it but I didn't use it for calls a lot till now. the problem happens when I join a phone call or VoIP like discord Instagram all of that, the audio quality gets lowered for media and the call, making it hard to hear the person. I've tested it with other headphone or earbuds and it does the same thing (all wired). I've tried clearing the cache of the phone and apps. using the separating audio it all doesn't work. but when I used the screen recorder it didn't have the distorted audio just a little crackles while joining then went back to normal. so its something to do with the output most likely.