Greetings,
I’ve tested the described WireGuard client behavior on RutOS 7.14.2 and wasn’t able to reproduce a similar issue; the tunnel successfully reconnects after restarting it via WebUI as well as after a reboot when using the WAN interface.
Could you please check whether this behavior still persists on your end with the 7.14.2 firmware installed (correct installation instructions are provided here)? Additionally, have you tried sending pings from the client’s peer to the server immediately after restarting the tunnel to see if it triggers a proper handshake and re-establishes the connection?
Best regards,