In this scenario, a large number of .mbox files were being discovered and converted to PST files. The discovery job was stopped and restarted, followed by a successful processing job.
A legitimate concern is within the Case Status page, where the 'Pre-Processing - Discovery and Scanning' job as stopped.
To verify that all .mbox mails have been discovered, select the source and run 'Discover new files for source', followed by 'Start processing source w/o Discovery'.
This will ensure that all Mbox files were processed and converted to PST's, in situations where a Discovery job was deliberately stopped.