CODA56 - Only getting 5.8Mbps uplink

On the NOW200 plan. Supposed to be 200/20 speeds.

I'm blowing past the 200Mbps downlink but the uplink almost seems like there's something that is actively preventing anything higher than 5.8Mbps. I say that because the downlink speed varies quite a bit (time of day, etc) but the uplink speed ALWAYS max out at 5.8Mbps w/o fail. It creeps up and then bounces back and forth between 5.7 and 5.8Mbps.

This is a owner-bought brand new CODA56. The previous is an Xfinity supplied modem that consistently gave about 25Mbps uplink speeds in tests.

I have access to the CODA56 admin page, but from what I understand about the different things there, nothing stands out. Signal levels look really good. (about 43dBmV)

Ideas?