Pasquale
Sep 22 17:14:34 <stm 304067> <ERRS> |AP 00111aaa051E:1647:4919@10.22.3.10 stm| PAPI_Send failed: papi_send_status_callback, 2731: Connection timed out; from 8451 to 216.123.55.169:8214 len 109 type 3092
this message is saying is that the AP 10.22.3.10 tried to send a message from AP STM (8451) to the controller AUTH (8214).. That should not time out, so yes, I would say that you have something going on, either between this AP and the controller, or if this message is more widespread across multiple APs, then more likely on the controller and specificlly involving AUTH.
Start by checking CPU, throttles, radius (or whatever back end auth is being used), security and user debug, 'show ipc statistics app-id 8214' etc.
By the way, for the captive portal in a hotspot like this, what is the model of controller here and is the httpd cpu running high ?
regards
-jeff