Using version 15.5 the system seems to hard lock as soon as I click the CDR option in the system settings. The CDR was empty as I had not done any calls yet. Currently using the Debian version of 3cx version 15.5 with all modules up-to-date. There were no server logs available to point to a reason. After placing a call that was not answered, I have been able to load the CDR web page with no problems.