Internet connection drops a few times per day

I had a tech visit last week to try and fix a jack. The coax in the jack turned out not to be Cox, so nothing was done with that. The tech did some work out on the box, and ever since the visit, my router drops the internet connection every few hours and shows this message in the system logs:

IGD[14598]: Eventing:PhysicalLinkStatus=Down

This is extremely frustrating. How can I fix this issue? My only thought was to factory reset the router and see what happens, but I can't help but think there was something done at the box to screw this up. I previously had practically zero service interruptions, and now I lose it so often, it's very disruptive.

EDIT: Wanted to add, after reading some other threads with similar issues, the tech did fix the jack where the router is connected. The jack was separated from the wall with another cable coming out, as well, and he cleaned that up. Just in case that might have caused an issue.