Typically, given all other conditions are fair, the client device disconnected from the radio. To really know why, it's best to see more of what happened Before & After the deauthenticated log entry.
Is there an overall issue you are looking into, or just exploring the Client Monitor tool?
Happy to help,
Be careful on using "Enable client load balancing among neighboring hive members for APs." It is only recommended for APs that can see each other such as in large meeting rooms with more than one AP or long halls with more than one AP. We have 5 locations on campus that uses it but no where else. Works very good in the auditorium. But when the APs are in different rooms it can cause issues and is not recommended.
we are also a community university with about 700 simutaneous accesses, in my case this change to force the devices to connect in 5 GHz was faulted about 15 days approximately and the reason that started this connection problem.
I made the change so that the AP will encourage the connection at 5 GHz and no longer force it. I also did the activation of the Enable client load balancing among neighboring hive members. for APs.