It's probably a coaxial issue, Can you copy and paste the modems signal level page from 192.168.0.1 or 192.168.100.1?
What lights are flashing?, what model is it?
You probably need to call TWC out.
I doubt it's the modem.
Possible preminary causes based on what you wrote, in order of what should be tried to be ruled out first with troubleshooting to last: