Unable to send full event to syslog

I'm trying to send Windows logs through Windows Event Forwarder, through Winlogbeat and Logstash to syslog. (System1->System2 with Winlogbeat->Logstash->syslog). For some reason event which appear in syslog is cropped only to message field, no event fields, no winlog fields. The same event in Elasticsearch has all of the fields. Why output to syslog on Logstash cropped fields other than message?