switch causes that AP sends out deauth with code 7

[hong zhang]

List,

My switch causes that AP sends out deauth with code 7.

Access points AP1311 and AP1250 on company network send out deauth with code 7 to all wifi stations every 30 minutes within a few seconds. 

Reason code 7 is Client attempted to transfer data before it was associated.

After updating switch firmware, this behavior is gone.

I heard this kind of things at least 3 times.

What will switch make that AP think stations are no longer associated with AP? 

Obviously, stations do not send disassociate messages.

---henry