1000/1000 Xfinity XB10 bridge mode - Speedtest 1050 down / 40 up

I have the 1Gig symetrical plan with XB10 gateway (bridge mode) and my own router and switch for my LAN. I onlny get ~40Mbps up. Sometimes it goes to ~600 MBps then drops down below 50 with no change by me. I went to Xfinity store to swap my gateway with no change. I asked tech support to send my gateway the backend rate codes/SOC codes and force-push the correct Next-Gen configuration file. Nothing changed.