When reviewing a log for errors the last few lines in the log contains:
! 10:02:05 Error: Failed to open document: (3637) Cannot convert MIME message to Notes Rich Text message.
! 10:02:05 Error: Notes error code: 3637 (hex 00000e35)
The error usually indicates that there are bad MIME data on a source documents preventing Notes from correctly reading the documents for migration.
The recommendation would be to run the migration again with a migration profile that has Verbose logging enabled and that should then record the NoteID or UNID for the source document to check checked in Notes.
One point to keep in mind is that the message is in the Unfiled part of the migration. That is a final check for All Documents in the source mail file to verify if there was any incorrectly filed documents that were not migrated in the correct folders such as Inbox or Sent items. So generally Unfiled migrations are documents that are not in a correct state to start with.
One suggestion would be to create a new replica of these mailboxes/archives(with same file name) and replace the original ones and re-migrate them. A new replica normally fixes the corruptions.
You can also run a command line Fixup and Compact of the database although the new replica is the recommended and preferred method.
If the issue persists please contact support.