You can try the KDETool PST to Outlook converter, which allows you to intelligently export all PST files at once, keep all email data unchanged, and export EMLX, MSG, PDF, HTML, etc. It extracts all-important email components such as To, Bcc, Cc, Sent, From, Receive, Attachments etc. All MS Outlook versions 2019, 2016, 2013, 2010 etc. are also supported.
VISIT HERE: https://www.kdetools.com/pst/mbox/
If you have the trouble with PST to MBOX Converter then I will suggest you try PST to MBOX Software it is a secure way to switch PST data into MBOX, EML, and MSG file format. With the help of a tool, you will never more wait and rapidly migrate to all of the data. Refer:- https://www.softwaretoconvert.com/pst-to-mbox/