OST to PST Converter
ATS OST to PST Converter will do the conversion of OST files into PST with Time Saving Tool.
* Restore single as well as multiple OST mailbox into PST files.
* Provide recovery of all the attachments including contacts and calendars.
*Saves mailbox items such as contacts, calendars, meetings, Inbox, deleted items, tasks, address book etic into outlook PST.
* Support saving recovered data into various file formats such as PST, MSG, MBOX, EMLX, EML, vCal, vCard etc.
Read More: https://ats-ost-to-pst-converter-toolkit.en.softonic.com/
I found an informative post which explains the free manual method and working third-party solution. In my case, the free solution worked well. You can also give it a try. Convert OST to PST for Free and save complete data into healthy PST format.
The listed methods will help you in these cases