I'm happy to help out here. It seems like, just from looking at the screenshot, the packet loss is beginning right at the second hop and is carrying through to the final hop (which means that we've probably found the culprit). I do see a *little* packet loss on that router - but a majority of the packet loss is coming from that second hop there.
I would recommend talking to Xfinity and letting them know that the IP at hop 2 is having a lot of packet loss issues. Xfinity can probably help you figure out what the device is at hop 2 (and spoiler: it's usually an ISP's demarc). Get in touch with them, and send them what you sent us (that image from PingPlotter). They might want to see the data itself, so don't uninstall PingPlotter yet!