Slow Connectivity (MB8600) 175mbps to 3mbps to 31mbps

Can't see your pics. Since you are a new poster, they need to be approved by a Forum Admin. That could take some time. In the interim, you could try hosting them at one of those free third-party pic hosting sites like Imgur or Photobucket and post the link to them here.

Here's the link to the photos: https://imgur.com/a/aFepwrv

O/k you've got some borked downstream channels there. Some of the SNR's are too low / out of spec. Seems there is some noise ingressing into the lines somewhere. First thing to try is power-cycling the modem several more times to see if it will lock on to a new perhaps cleaner set of channels.

The channels have remained to be the same frequencies.. Still a problem.

Here's some stuff that you can try but you may need a tech out to investigate this one;

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.

Thanks EG. I will try that. I live in a townhome and there's 6 additional units so I assume (?) all the wires go to the same place. 

Thanks for the help.

Edit: I see a scheduled maintenance for my area on 4/16. What does comcast do on their "scheduled maintenance"?