Hi Johnny,Do both the CAPWAP data and management tunnels stay up?Run the following on the WLC next time you have the issue: show wireless dtls connections 

Hi Johnny,Do you know what is triggering this behavior? As we have similar strange behavior, in which our sites failover to the backup connection and the CAPWAP tunnels between AP and WLC move into a NULL state 

I think we also had the same problem not so long ago, it was the way in which ISE was classifying the Avaya handsets. I'm sure we profiled the Avaya handsets using the MAC address and this temporarily fixed the issue whilst we looked for a more perma...