Internet dropping every few hours, lost packages, intermittent connection (few years already)

We have to be very careful reading the results of ping against public websites (or public DNS), the website may be a server farm where not all servers are configured to respond to pings from the public internet.

It is unusual to see the DOCSIS 3.0 power levels range from -0.4 to 3.7 dBmV  they are all in the preferred range & SNR is very good, but on one connection the power figures are usually all much closer.