I've been having this issue shortly after I got my phone in August.
Suddenly the volume in the earpiece has dropped to a very low setting. The slider shows its max and pressing the volume up button doesn't increase it. The only way I can hear a person during a phonecall is thru my Bluetooth earpiece.
I've tried clearing the cache and data for the phone and restarting the phone, I've upgraded to Android Pie and still have this issue.
I'm still waiting for Nokia tech support to reopen my previous case but that hasn't happened for over a week already.
I love this phone and would hate to get something else because of this issue.
I have the TA-1068 model and bought it new from Amazon.ca.