R6230 Ethernet connected laptop speed dropped by 50%

I bought a Netgear R6230 Router to use with my Netgear CM700 Modem. I plugged it all in with Ethernet cords a few months ago and everything worked fine. All of a sudden my Ethernet connected speed dropped from 950 Mbps to 400 Mbps. Then I plug my Laptop directly into the CM700 the speed goes back up to 950 Mbps, I've done factory resets and reboots several times to no avail. Any ideas on what might be wrong?