C7800

you're upstream power levels are low and you have errors in your line. 

Remove any splitters, attenuators, amplifiers from your line. Prefereably connect the C7800 directly where the line comes into your home. this ensures that the lines within your home aren't the issue. If that's not possible, inspect your lines for kinks, worn coax, loose connetors, cheap connectors, water damage or water within your line, nicks, etc.  

If you're directly connected with good connections and you're still getting these results, have your isp check your line. Something isn't correct with your incoming/outgoing signals. 

this i the forum for the C7800

https://community.netgear.com/t5/Cable-Modems-Routers/bd-p/home-cable-modems-routers