IPv6 Service Broken After Upgrading Internet Speed and Changing Gateways from CG3000DCR to CGA4131CO

I had 150 mbps service with a Netgear CG3000DCR and IPv6 with DHCPv6-PD worked flawlessly with my Cisco router. I decided to upgrade my service to 300 mbps and, of course, the CG3000DCR will not work with the higher speed. A technician came out to replace the CG3000DCR with a CGA4131COM for the speed upgrade. Nice that that I was able to have my phone service and Internet service on one device instead of two. The installation went smoothly and Internet and phone service is working well. Except for IPv6. After the gateway swap, IPv6 DHCPv6-PD is broken. I can do IPv6 pings and traceroutes with my Cisco router (for example Google's DNS server 2001:4860:4860::8888) with no issues. However, even with clients automatically getting IPv6 addresses, no IPv6 pings, traceroutes, or traffic will pass through or route with the CGA4131COM gateway from clients.

I have read numerous posts in the IPv6 forum and online that this is a known problem with the CGA4131COM Comcast Business gateway. I have read that the DPC3941B Comcast Business gateway MAY solve this problem. This is a big show stopper for me. Since I have five static IPv4 IP's that I would have a hard time to give up, bridge mode is absolutely not an option. I have posted this information in the IPV6 forum and no response from Comcast. I called support regarding this and they are clueless what the problem is. If the problem with the new gateway cannot be resolved, perhaps trying a DPC3941B and going back to an Arris voice gateway may be the answer. If that doesn't work, I will have to go back to 150 mbps Internet service, go back to the Netgear CG3000DCR gateway, and go back to the Arris voice gateway. I do not feel that I should have to pay for a service call to go back to my previous speed service and equipment if the problem cannot be resolved. Having IPv6 is that important.