Thanks for confirming your setup, can you please also let me know the model/manufacturer for your Router and Access Point that the CCA is connected to? The IBM switch that you mention seems like it’s a managed switch, we have had reports from Users indicating that managed switches require a bit more setup than regular switches to communicate properly.
Can you please double check your Multicast settings on the switch, router and access point, and see if you have the option to enable “IGMP Proxying” and “Flow Control”. There are a few more suggestions for managed switches/access points on our Network Best Practices guide, linked here: https://kb.roonlabs.com/Networking_Best_Practices#Router_Specific_Settings.
You can also read more about the Flow Control settings in these threads:
Please let me know if any of my suggestions resolve the issue at hand.