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":
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.