Hello,
Try setting Static Route rules, for RUT240 in Network > Routing > Statis Routes choose interface, in your case it should be openVPN, write in Destination address of another end of tunnel, e.g. if yours server LAN IP is 192.168.1.1 enter 192.168.1.0 enter Netmask, most likely 255.255.255.0, for Gateway write in Server IP (OpenVPN virtual IP or Server LAN IP)
For server do the same just replace Destination address and Gateway with RUT240 LAN IP and IP
That should do the trick.
Best regards,
VidasKac.