Internet keeps dropping and reconnecting, as well as lagging.

I use a desktop computer at my home and its connected to the nearby router by ethernet, ever since I got this modem the internet will cut out at random times in the day for anywhere from 1-5 minutes or spike in lag several times a minute. The equipment I'm using is what was provided by Xfinity, and I have had technicians out three times to replace the wiring and router itself so all of it is brand new and should be working. 

I checked my event logs and saw this: