Hello @Andrew_Webb,
Thanks for updating me regarding the issue.
We have previously seen reports that unchecking Disable IGMP Proxying in Orbi routers improve communication in cases like this. Can you please try changing this setting from the Router’s configuration page and let me know if this helps resolve the issue?
I would also make sure that these ports are set up for proper access on the Router & Core’s Firewall:
I look forward to hearing your findings after doing so and if you have any questions/difficulties just let me know.
Thanks,
Noris