My Deco throttles my speeds down to approximately 120-150MB down and 9-10MB up.  I've had Cox technician visit my house just now because the speed has been an issue for several weeks.  He tested the directly from the cable modem and it was consistently 550-600MB down and 55-60MB up.  As soon as he connected his test device to the router, it would fluctuate 300MB to 130M down and 30MB to 9MB up before settleing at 140MB down and 9MB up.

I've tried resetting the router multiple times, power cycling, and replacing the network cables.  Nothing seems to fix the problem.  This wasn't an issue a few months ago, but the only thing I can assume is that some new firmware is causing this or the router is no longer functioning as intended.  Please help.

Do I need warranty replacement?