A network interruption during synchronization can damage your OST files, especially if Outlook is updating data when the connection drops. As a result of this, emails, contacts, and attachments can get damaged or inaccessible. To try to recover OST file data, I would recommend OST recovery software. I am using 
FixVare OST Converter software because it can recover OST file data and save it into various formats such as OST & EML. It provides an easy way to recover OST files and maintain folder hierarchy, and is compatible with all Windows and MS Outlook editions.