Have a look at this thread, another users had a similar alarm: https://community.cambiumnetworks.com/t5/cnMaestro/Wi-Fi-clients-events-are-blocked-as-device-generating-high-rate/td-p/93559
This alarm means that 50 connect/disconnect events have been received within 5 minutes for a single client, this is unusual and I would personally try to locate the client and troubleshoot it.