Thanks for the reply and providing detailed system requirements and docker stats. Seems I missed the note in the README. :-)
Actually I am not really using syslog per say, but systemd journalctl which default behaviour on Debian (rsyslog) also duplicates to /var/log/syslog.
StandardOutput=journal
StandardError=journal
Is there a better integration to pull logs from my systemd services and journalctl up to HyperDX?