OpenVPN fails after failover to upgraded node (25.1.7)

[ajr]

I upgraded may backup node and then did a failover to (persistent CARP switch) to upgrade the old master.
The OpenVPN client could not create a tunnel.
I switched back to the old master (running 25.1.5_5) and the tunnel came up.

Does the OpenVPN configuration needs a change with 25.1.7, related to (from README):
  openvpn: add port-share as advanced feature
  openvpn: add (push) block-ipv6 option
?

Is this a known bug ?

What else can I do to resolve the issue ?

ajr