Internet dropping at random intervals

I had this issue before however with a different ISP/MODEM/ROUTER setup and it ended up being a bad/corroded splitter. Replaced the splitter and problem dissapeared.

Once on a DSL connection I had same issue, the problem was outside in a phone line junction box. We took the incomming pairs and swapped them to an unused jumper pair and it worked just fine after that.

Oxidation and Corosion cause db losses and that messes up a lot of things.

You can try swapping in a new modem or take this one to a friends house that has the same service and verify it is good or bad.

Thats the best way to verify the modem.....