I'm seeing the connection to the VPN gateway failing in our Network Extension (not a System Extension) most of the time. Sometimes it succeeds. There's no difference in what the application or the extension are doing in the two cases.
I can't see a pattern to when it fails, but In the console I see different messages. The only thing I've seen showing up consistently on failures but not successes is the message about the swfs_pid_entry.
On failure:
vpn_extension Gateway address 10.10.10.10, port 443
kernel ALF, old data swfs_pid_entry <private>, updaterules_msg <private>, updaterules_state <private>
vpn_extension connect failed with error 65 (No route to host)
kernel connect() - failed necp_set_socket_domain_attributes
vpn_extension Connect returncode 65
On success:
vpn_extension Gateway address 10.10.10.10, port 443
trustd User has disabled system data installation.