Screenshot from the WebUI
Maybe also good to mention that the Android device I'm on right now is connected to the Slate AX and shows 192.168.8.1 as the configured DNS server, which is the IP of Slate AX.
When I change the DNS settings to manual in the Slate AX menu and configure 10.x.x.x as the manual DNS server I'm no longer able to resolve DNS requests. I can still access hosts on the other VPN lan based on their IP. Clients running in the other (VPN) LAN and are configured to use the 10.x.x.x DNS server have no problems resolving hosts.
Hope this helps identify the issue.