[SR-Users] Disconnection from Kamailio

Greetings. I observe strange behavior with Kamailio. My iphone 3gs run softphone based on resiprocate. First 10-20 minutes everything works fine. After it the connection is closed from server (select() loop returns read notification, read attempt returns zero bytes). Ok, softphone closes old socket and create new one by new registration. But this connection is terminated from server in 4-5 seconds after registration finish (200 OK). Softphone makes next attempt to register - connection is closed after registration again. So it is infinite loop. After several attempts iOS kills application as it awakes too often in background mode. I have not logs from server yet; but maybe anyone had similar issue? Thank you :)