RS700 losing internet connectivity

I have a similar issue.   I installed the RS700 last month.  Newly connect devices connect to WiFi and internal network instantly but take another 1 to 2 minutes before they have internet connectivity.      

Once internet connectivity is established, we are having issues with the intermittently losing internet connectivity, which causes our VoIP phones to drop calls, etc. etc.

Multiple calls to the help desk and multiple reboots and factory setting reboots have not solved the problem.    

We are about to go back to a N600 to get us by until we find a solution or a new router.