Are you relying on automatic configuration of port forwarding via UPnP/NAT-PMP in the Settings → ARC page? If so, then it’s expected that the port forwarding would need to reconfigure if either RoonServer, the router, or the network connection temporarily shuts down.
Please share a screenshot of the ARC settings page in Roon.
If you’ve manually assigned a port in the Settings page and in your BT Home Hub, then RoonServer should retain the same port on each startup.
RoonServer will close on a laptop if the machine hibernates due to battery cycle or a closed lid. Some users install third-party apps like Amphetimine to keep RoonServer awake when this happens.
Thanks Connor - been running your solutions for a week now - software updates and ampethimine app seem to have solved things - thanks again for the help