internet hiccups

This has been going on for several months now. Sometimes the internet would be fine for multiple hours or a whole day; sometimes the connection drops for 30 to 120 seconds before going back, being up for 10 or 20 minutes, and dropping again, so needless to say, it makes any online gaming an unbearable experience. I didn't notice any specific time slot related to this. Power cycling the modem only helps occassionally for a few hours, other times it doesn't do much at all.

I managed to take some screenshots form my modem during one of these episodes:

https://imgur.com/bUzNb5e

https://imgur.com/uZzNCUi

https://imgur.com/9wC53mO

https://imgur.com/TTO8JBi

https://imgur.com/r5YFu5Q

https://imgur.com/F3fR2bC

I tried to track the cable to my wall outlet. It goes underneath the floor of my house and then over one of my neighbor's roof, so I can only assume that it goes towards a pole; nevertheless, I did not find any splitters on the line. My computer, my router, and my modem are connected via ethernet cables. Replacing the coaxial cable with an unused one didn't help. Any idea what might be going on? Thanks.