SNAT Traffic is not working with Dual Stack (IPv4 & IPv6) Router Configuration.

Steps to be followed the Dual Stack Configuration.

1) Create Network 1
2) Create IPv4 Subnet under Network 1
3) Create IPv6 Subnet under Network 1
4) Create Neutron Router 1
5) Attach IPv4 and IPv6 Subnets to Router 1
6) Boot VMs from the Network 1
7) Create External Network with provider type GRE
8) Create IPv4 External Subnet for IPv4 NATing
9) Create L3BGP-VPN (Internet) Instance
10) Associate L3BGP-VPN instance to External Network
11) Attach External network to Neutron Router 1 (Using Router Gateway Set command)
12) Initiate SNAT (External Network) traffic from Dual Stack VM

SNAT IP + Port translation at Table 46 is failing with result that SNAT traffic is not working for dual stack VMs.

Expected Behaviour: IPv4 NAT traffic should work with dual stack router configuration.