Packet loss, latency, and serious fluctuation in internet speeds.

I received new comcast modem model CGM4140COM just a couple months ago.

 

Everything was working okay, until suddenly I started getting serious packet loss while gaming on my PS4 console. This was not happening with my old modem/router combination, and nothing has changed since then regarding the hardware setup. 

 

The PS4 is hard-wired to the gateway via ethernet. 

The internet speeds are fine according to tests on PS4, Comcast website, and google (>200Mbps download, 10Mbps upload), ALTHOUGH I have noticed SEVERE changes in internet speeds for aparently no reason. 

 

I have tried opening a port on the gateway, resetting/restarting the gateway, new COAX cable, new ethernet cables.

I have tried putting the modem in "Bridge Mode" and using a different router, but get the same result. 

In fact, now my modem/router combo is STUCK in bridge mode, according to Comcast website!

 

Extremely frustrating, especially since I am sent in circles when I try and get in touch with anyone at Comcast to help fix the issue. The recorded messages send you in circles, and only offer to reset the modem. 

 

I found this article, which mentions the issue was damage to a "node box":

https://forums.xfinity.com/t5/Your-Home-Network/Packet-Loss-and-Latency-Spikes-Online-Chat-and-Games/m-p/3253512/highlight/true#M306495

 

I also found this article using the same modem, to which there was no solution found, and this person had tried even more approaches than me. 

https://forums.cox.com/forum_home/internet_forum/f/internet-forum/23408/very-odd-issue---ipv6-firewall-causing-unbearable-packet-loss

 

Please help!