Thanks for reaching out, @Neil_James!
So we can better assist 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.
Is there any difference in how these two Node 2s are connected to the network?
Have you tried rebooting your Core machine and networking hardware since adding the second Node 2?