Hey @Gareth_Irwin — Thanks for reaching out to us!
So we can better assist you, may I ask that you please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so we can have a clear understanding of how your devices are communicating.
Additionally, can you try giving the Core machine a reboot and see if there is any change in behavior here?
Thanks!
Dylan