During migration the following error may be seen in the log file.
12.55.56 ERROR:[1211-174-21-00000000] Problem encountered with worker program
12:55:56 Unresolved workitem found for (D3727CC2-DD25-492A-98CC-61F7B1F3C1AA)(MAIL\\nw001\V$\NSF\mail\nwnsf001.nsf)
12:55:56 DEBUG: Remove unresolved workitem from cache for user email@example.com: MAIL\\nw001\V$\NSF\mail\nwnsf001.nsf
A particular message may be corrupt, causing the migration to fail for that message.
Shortly before the above you could find information ragarding the failing message:
12:54:36 DEBUG: NotesExportOneMsgItem (TYPE_TIME) DeliveredDate ==> (0X0054225A123)
12:54:36 DEBUG: NotesSrc::TimeDate2Time_t - TIME 20:25:00 ZONEINFO 00
12:54:36 DEBUG: AddTextItem: internetmsgid => <firstname.lastname@example.org> (45)
12:54:36 DEBUG: Exporting mime for Subject-Line
12:54:36 DEBUG: NotesSrc::ExportOneAttachmentList()
12:54:36 DEBUG: NotesSrc::ExportOneAttachmentList() - Adding attachment filename.ext (C:\DOCUME~1\userx\LOCALS~1\Temp\ATT0CB404C3.tmp)
With this information you should be able to find the message in the nsf file using the Notes Client. Please try to access that message and - if applicable - the attachment and have a look at possible issues. If you are not able to solve the issues, you could try to remigrate the nsf file without that particular message.
Ensure that any antivirus software is not set to "active scan" the data when the migration is running.