Fios one way voice traffic over ipsec-nat-t

[Louie9]

I'm having problems with voice traffic over ipsec-nat-t  across Verizon Fios. I'm using WiFi calling on my Verizon iPhone 6 and a voice over ip phone running over a VPN (two separate ipsec tunnels).  When I make a phone call, people can hear me but I can't hear them. I used Wireshark to capture the traffic at the ethernet port of the Verizon provided Actiontec modem model MI424WR-GEN3I. I see many 302 byte ipsec-nat-t packets heading out towards the internet but no return packets. But I do see transmit and receive packets over the ipsec-nat-t tunnel for data traffic (Web, email etc). I brought my VPN equipment and iPhone 6 to a neighbor's house that uses a non Verzion internet service provider and everything works.  This was working up until 6 weeks ago.