It seems I have the same issue in "CSeq issues with CANCEL after INVITE #918".
The "CANCEL" is followed by "500 Server Error" from provider due to
incorrect CSeq. Only happens when canceling the call before it's answered.
--
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/kamailio/kamailio/issues/870#issuecomment-271158070