Your pictures are broken. FWIW do not run ICMP packet based pings to the Comcast DNS servers as they are deliberately configured to de-prioritize these probes. Choose other targets like sites that you are having a problem with, your Comcast WAN default gateway address, or google.com etc.
I understand pinging internals ie the the cmts, dns servers, or any other internals with have a skewed result. But pinging somewhere like yahoo.com, google.com, and or the gateway ip yields the same loss and spikes.
The signal stats look. The modem's RF error log entries would be helpful. I don't have a CC gateway device so I can't tell you where to look for them, sorry. Is this with a WiFi connection ? If so, for a test, does a computer hardwired directly to the router / gateway device with an ethernet cable have the same problem ?
Using a utility for TRACEROUTE to the IP addresses might show which leg is having issues. It could be there is a router along the way from your location that is having issues.
Using the command prompt TRACERT on my desktop:
C:\Users\Joe> tracert 188.8.131.52
I am not using wifi, the computer is cat 5 to the arris gateway. I don't think this gateway gives the end user access to the RF log.
I'm going to try escalating your issue to the Comcast corporate employees that are available to these boards. You should get a reply here in your topic.