Poor quality of outgoing calls (voLTE, voWiFi) Zenfone 8

[NewAje]

Suddenly in past weeks my Zenfone 8 incoming or outgoing phone calls sound like underwater, cannot understand each other. It was working fine for months before that and it worked again for a few days but now is back to can't understand callers. I use a 2nd Zenfone 8 with same carrier Mint Mobile which uses Tmobile network. I read another post about problem with some codec support on Zenfone 8 on T-Mobile. Why would it happen on some Zenfones and not others? I have a 3rd ZF8 I can transfer but prefer to try to resolve this one, without or with doing factory reset. Please advise. 

[kmcmurtrie]

Did the new Google AI noise cancellation turn on?  That feature is completely broken for me. It chops up the sound.

[NewAje]

I have not seen the Google AI noise cancellation option or feature so far. Even if I mute the call I cannot understand the caller either. Also I tried the SIM card in my old Google Pixel 4a and it works fine there. Also noticed the calls sound fine when I am at other locations away from home. It's just at home that this issue seems to be ongoing, very frustrating. Since I got these phones used from Ebay and Mint Mobile does not officially support them, I may be SOL. The other ZF8 phone works perfect, in the same location. I have a feeling there is a way to tweak the settings to get this resolved. 

[NewAje]

Update: When I switch the phone to 4G only or 4G/5G only mode, I still have data but cannot make calls, it ends the call right when I try to start a call. Seems this phone may not have the proper 4G radio for United States, maybe it's an Intl version. Going to swap phones and factory reset to see if any change occurs.