Problems with the speed...another one.

Here is my problem 😞

I upgraded to Gig-speed with Comcast and, of course , I'm barely getting half of the speed I'm paying for (~400 Mbps ). My set up is the following:

Coaxial cable comes from the outside into my modem (Not longer than 8 feet of cable until it reaches my modem, which is a Netgear CM1000) --> Nighthawk X6S ac4000 router --> wired connection to the computer.

I called Comcast, and after the normal trouble shooting guide, they send a tech over. The tech connected the coaxial cable straight into his device, and it gives him an internet speed of ~1.2 Gigs. So the connection into my house seems to be in working order.

Now, after searching forums and the interweb, I found lots of post on the same issue, but none of them gave the correct fix. i also did the troubleshooting guide from Comcast forums. i connected the computer straight into the modem, skipping the router, and im still getting around ~400 Mbps. Upon checking my modem;s event log, i find for what i believe, too many T3 and T4 errors images . Is this amount of errors normal? who can i call or how can i fix my internet speed issue. also in the folder, the cable connections settings in my modem.