Ok, so now I have been re-educated again!! Your terminologies are a very new to this OLD Tech with over 42 plus YEARS of doing this stuff!!
I now know a new term EMTA!!"Modems with Embedded Multimedia Terminal Adapters are cable modems with an analog-to-digital telephone adapter integrated with the modem’s cable network access hardware. This allows the cable modem to utilize analog phones with a cable provider’s Voice Over IP services."
With this new found bit of information it give me a little more to investigate.
If it were not for a customer with ultra sensitive hearing this would not have been on my list of things to learn. Troubleshooting will be a very extra challenge with my deaf in one ear and can't hear out of the other issues. But, I will see what I can do by making a few changes with what I can see.
I may have to just throw it to Comcast and see if they can point at anything other that the phone equipment.
That will depend on the knowledge of their Tech!!
Maybe try and convince them to install another Modem could prove or disprove it was the problem??
Thanks for the extra insight!! Very helpful!!