So I wanted to just let you know that IPVanish and other VPN providers are totally unsafe. When you lose connection to the VPN if your not taking extra steps, and they do not tell you this, your private IP is exposed. So whenever they have a flap or a ddos or momentary downtime, your exposed. Something you all should consider when trusting these companies.
VPNs, even in the vanilla OpenVPN app, should not silently fail and fail over to your regular connection. If this is happening, you should contact your VPN provider.
The only case where I can think this would happen is if the problem is between your PC and your router. DHCP could overwrite the routing table that was modified by the VPN. Even then the --redirect def1 option should cause the connection to fail rather than allow traffic.
I know that there are Windows applications that disconnects your internet connection when you’re disconnected from your VPN (this is called killswitch). I don’t know if they’re reliable though.