Internet slowing waydown, intermittent

There are some borked downstream channels that have out of spec SNR's. Seems like there is some extraneous noise ingressing into the line(s) somewhere. You can try this stuff but you may need a tech out;

In a self troubleshooting effort to try to obtain better connectivity, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Then get a tech out as stated earlier to investigate / correct the problem.

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.

Good luck with it !

Hello jnowakphoto, thank you for reaching out to us here with this concern. I wanted to circle back to see if this issue has been resolved, if not please send me a private message by clicking on my name then click "Send a message". 

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards.  You should get a reply here in your topic. Good luck !

Glad you got it sorted. Wonder how the original poster is making out ?

Hello and thank you for replying here, I apologize for my delay in response. For further assistance please send me a private message with your full name and account number. We can take a look at your signal levels to see if a provisioning is needed to resolve your issue.