What are Access-points that you are using?
I notice that it works fine with 1600, 2600 and 3600. Clients are deleted with reason code 4:
*spamApTask0: Oct 19 17:31:09.203: 00:23:14:81:e6:80 Received DELETE mobile, reason MN_IDLE_TIMEOUT, from AP 54:4a:00:2a:47:60, slot 1 ...cleaning up mscb
*spamApTask0: Oct 19 17:31:09.204: 00:23:14:81:e6:80 apfMsDeleteByMscb Scheduling mobile for deletion with deleteReason 4, reasonCode 4
But in APs 1130 and 1240AG the same clients are not signaled as "Sleepy Clients" and are deleted with reason code 15:
*spamApTask3: Oct 19 16:06:33.234: 00:23:14:81:e6:80 Received DELETE mobile, reason UNKNOWN, from AP 00:26:98:fe:8f:90, slot 0 ...cleaning up mscb
*spamApTask3: Oct 19 16:06:33.234: 00:23:14:81:e6:80 apfMsDeleteByMscb Scheduling mobile for deletion with deleteReason 15, reasonCode 1
*spamApTask3: Oct 19 16:06:33.235: 00:23:14:81:e6:80 Scheduling deletion of Mobile Station: (callerId: 30) in 1 seconds
Cheers,
Vasco