Phalcon is compiled into a C extension loaded on your web server. Because of that, bugs lead to segmentation faults, causing Phalcon to crash some of your web server processes.
For debugging these segmentation faults a stacktrace is required. Creating a stack trace requires a special build of php and some steps need to be done to generate a trace that allows the Phalcon team to debug this behavior.
Please follow this guide to understand how to generate the backtrace.