Low volume XG1v4

I am just following up on this existing closed post: https://forums.xfinity.com/conversations/x1/low-volume-on-xg1v4/61d71863f069681686044893

I just bought a 4K tv and got XG1v4 box instead of my older 1080p one, and while I connect the box via HDMI 2.1 to the TV and use optical cable from TV to A/V received (the same setup I had with the old box), the audio volume comes up really really low. I really need to push double the volume from the receiver to get the same sound I used to get before cable box replacement. YouTube app within the Xfinity box produces much louder volume than cable channels. So something is just wrong in how audio volume is handled by the XG1v4 box. 

I don't see any updates on this topic in the past 8 months.