Problems with NETGEAR N900 (CG4500BD) Combination DOCSIS 3.0 MOdem/Dual Band WiFi Router

So I wanted to get the faster Internet speeds that I have been paying for and was told to get a DOCSIS 3.0 modem.  I noted that I could get a combo modem/router which would eliminate a box so I thought, what the heck - let's do it.  I bought the N900/CG4500BD directly from Cox and installed it in November.  I have had nothing but trouble with my WiFi since.  Sometimes, only the 2.4 GHz channel is lit up and works.  If I reset the WiFi Router with the button on the front face, then sometimes I get both and sometimes only the 2.4 GHz or the 5 GHz channel.  Then sometimes, despite the fact that the lights are on, there is no WiFi signal whatsoever which forces me to rest the router again.  This happens every few days and sometimes, seemingly randomly, more than once in a day.  I called Cox and the tech had me do a factory reset of the modem/router which solves the problem for awhile but then within days or hours, we lose WiFi again.  I called Cox and had a technician come out.  He agreed that something was wrong but since he and the person on the phone at Cox couldn't figure it out, he decided to swap out the device and give me a brand new one.  Same thing happens.  Mind you, the wired portion of the modem seems to work.  Just the WiFi disappears randomly requiring a reset of the router.  Once, a couple of weeks ago, the reset didn't even work and I had to the factory reset of this unit as well.  Same results.  WiFi signals randomly disappear (they never reappear without a reset), often only one channel is lit and working when it does work.  I note that previously with my DOCSIS 2.0 modem, I had a NETGEAR Dual Band Router connected to the modem for my WiFi and we NEVER had any problems with the WiFi.  SO while some have said that maybe something is interfering with the WiFi signal, that wasn't the case prior to getting the combo modem/router.

Any ideas?  I'm ready to chuck the *** thing and buy a separate modem and go back to my old router which at least worked.