1) Set the Core Log Level to DEBUG and save.
2) Edit every SIP profile involved in the issue you are getting logs for and ENABLE SIP TRACE.
3) Go to System->Reports->Network->Network Capture. Then click Capture and reproduce your issue.
4) Stop the trace once the issue is reproduced and download the wireshark trace.
5) Go to Backup - Restore, then click Backup.
6) Select Support Backup as the backup type, then click backup and download the backup.
Send in both the Support Backup (from step #6) and wireshark trace (from step #4) to support.