So many things can go wrong in Real Time Communication, and most of them are not your responsibility, nor are in your reach. Can be a faulty switch in your Internet Carrier, a misconfiguration in ITSP, a phone faulty firmware, a customer firewall, your datacenter new topology.
And, obviously, can be an error in your implementation of any of the techniques we saw in previous chapters. Or, maybe you're right, and is a bug in a FreeSWITCH module.
Following sections are about how to troubleshoot your FreeSWITCH implementation, so to understand what the problem is, and where it comes from.
For more details and techniques please read the chapter "Tracing and Debugging VoIP" in "Mastering FreeSWITCH" book, Packt Publishing, 2016.