The bug is in Asterisk. It has problems with the encoding and pass that along via the manager event. FOP2 cannot fix encoding issues or invalid strings, as it does not know in advance what the problem might be. I already replied to your ticket about the issue, it is a bug in Asterisk and it must be addressed in Asterisk. FOP2 already supports UTF-8 strings and handles them correctly for conference participants, IF the callerid string is valid in AMI events. If the string is wrong. and you also see errors in the asterisk cli about it, then it will have issues... Decoding the callerid in your example leads to a null character at the end, that breaks the json string. The null comes from Asterisk. That null is NOT shown on other events with the same callerid, like queue member events, so it seems to be a bug particular to conferences.
Best regards,
