I am developing a VoIP client for S60 3rd Edition FP1. I found a strange issue of SIP Server crash with E32USER-CBase 21 when keeping Registration expiry time to 30 or 60 seconds. Register has a Refresh enabled and SIP Stack sends Register refresh request every 15/30 seconds. On receiving Register request Call manager sends 2 Subscription request for which VoIP client sends 200 OK and Notify. For testing purpose no Subscribe request is sent from VoIP client to Call Manager.

If any VoIP call is active then after some time, SIP Server crashes with E32USER-CBase 21 error code. From SIP packet trace it is found that for Registration refresh request, call manager sends 200 OK with different "To-Tag". Has anybody ever faced such issue with SIP Stack? How can this issue be debug? Please help!!!