I also selected "ignore automatically obtained routes" and "use this connection only for resources on this network". The gateway was the remote open VPN server's private IP address. I'm also using a TAP device. The open VPN server gives the client an address in its pool of addresses.
I got around this problem by adding a route on the IPv4 tab when editing the VPN connection. The route I added was
address: 172.x.y.0
netmask: 255.255.255.0
gateway: 172.x.y.117
metric: 1000
I also selected "ignore automatically obtained routes" and "use this connection only for resources on this network". The gateway was the remote open VPN server's private IP address. I'm also using a TAP device. The open VPN server gives the client an address in its pool of addresses.
Regards,
Daniel