The end of the mystery appears to be in the treatment of traffic nearing pp.ringcentral.com from the external IP of the MX67 which is provided by Comcast. And the issue may involve multiple sites as we use Comcast a lot. I'll ask a troubleshooting specific to this kind of suspected asymmetric traffic problem. I've dealt with a couple in the past but man it's time consuming and frustrating.
... View more