Empty PDF file is generated by Scheduled Reports

Sometimes an empty PDF is created.
When Scheduled Reports created a PDF every day, sometimes it succeeds and sometimes it fails.
To confirm, I duplicated the settings and created the same report every minute.

Steps to reproduce:

1. Duplicated the Scheduled Reports settings and changed only the name and start time.
   See screenshots (image-1.png and image-2.png).
2. Wait until the start time and receive reports.

Result:

  One succeeds, the other fails.
  A. Success pattern
      PDF file is output correctly. See following files.
      ・daily_report_230-zbxsv_3_2022-03-14_15-10.pdf: Generated PDF file
      ・zabbix_server.log.1: debug log
      ・1647238213.Vfd00I1cee7eM480461.zbxsv230: Received email
  B. Failed pattern
      PDF file is empty. See following files.
      ・daily_report_230-zbxsv_8_2022-03-14_15-15.pdf: Generated PDF file
      ・zabbix_server.log.2: debug log
      ・1647238502.Vfd00I1d52c2M824369.zbxsv230: Received email