Here I would also like to refer a manual OST to PST conversion solution-

- Open MS Outlook -> go to File Menu -> Select 'Export to a file' option -> click on next button
- Select PST file and then click on Next button
- Select folders you want to export, then click on the next step
- Choose the destination location and click on the finish button to exit from the export wizard

For more help, visit- https://ostconversions.blogspot.com/2014/09/resolve-ost-error-issues-and-retrieve-its-data-by-converting-into-pst.html