[Freeswitch-users] SIP timer at 900 seconds?

I see two recent calls from FreeSWITCH that end at 15 minutes: billsec: 904.1, hangup cause: MANDATORY_IE_MISSING billsec: 901.3, hangup cause: MANDATORY_IE_MISSING My system is hanging up the call. Is there some sort of SIP timer? I don't have a SIP trace to see what happened. The remote carrier said:

However I'm unsure of what the issue is you are reporting as the BYE simply came from your side? This is not something we are familiar with or why your server did or requires this. Reason: SIP;cause=488;text="No answer to offer".

Any suggestions? -Avi Marcus