Lot of Disconnections with Zyxel AP Nebulla "deauth by STA Logout"

Hi All, 

I hope somebody can help me.

We have a lot of disconnections from our devices and I see in the logs the message deauth by STA Logout and Reason 3. The device is a Zebra PAD for inventory.

My Laptop is OK and my smartphone also. But still issues with all PAD devices.

I ve tried PAD device connected with an other Access point constructor (Autonom mode) and its working fone

ANy ideas pls ?

Thanks in advance for your help. 

Regards,

Mathieu Lopin