Want my old modem back

About a year ago I was hounded and finally convinced to upgrade my older black router/modem to the new white one (model number Tg4482a). We have had nothing but issues with this one since it was installed. About 2-3 times a week it will disconnect itself and need to be restarted. The old model we had NEVER had this issue in the two years we owned it (sitting in the same location in the same house). We've had this one for over a year and have experienced nothing but trouble.

In addition to the disconnects the speeds seem to be throttled at times. I used to get consistent 800mb/s download on an ethernet connected desktop whereas now I struggle to get above 500. My roommate connects his laptop via wifi and struggles to get over 10mb/s download where he used to get around 100. We pay for the GB plan.

Before it is asked, yes I've checked the connections for tightness. Ive replaced the coaxial cable, I've changed the outlet and powerstrip it was plugged into, and I've changed locations for the router (it has since been moved back). None of those changed anything.

During times the connection drops there have never been any outages reported in our area. Between that, and the fact that this only started happening when we got the "upgrade" to the new router, im assuming that it is one of two things. Either this particular unit (or this entire model line) is faulty, or someone at comcast is trolling us to see how much we can put up with before we complain.

Please advise on how I can replace this unit.