Any fixes to Modem Issues with Gigablast.

I’ve been reading that many people are experiencing slow gigablast speeds hardwired. My situation is almost the same. Got gigablast and bought a shiny new nighthawk CM1200 modem to go along nicely with it. To my disappointment and to many others, I was only able to pull 300–350 hardwired directly into the modem. Had techs come out to replace everything from the street to the house, we ran a test with the new coaxial and we got The full 1Gb. Now I connected it to the modem  and hardwired it my ASUS ROG laptop and boom! 300mbps....what a let down. 

has anyone every got this issue resolved???? I’ve seen many posts but no solutions! I’m thinking that the modem was not configured correctly by Cox or it’s possibly a bad modem? 

kinda sad when I’m getting almost the same speeds I Was getting before on 150 preferred. Oh well I can always go back, I got my trusty Arrias SB1693 on standby.