When attempting a "migration session" and moving an OU structure to the target which has the identical OU structure, the tool will fail to place or merge objects into their matching OU.
The result is objects migration failed with error, as following:
Error 0xe30000a4. Object: LDAP://DC.SouceDomain.Com/CN=Child1A User1,OU=Child1A,OU=Child1,OU=ParentOU,DC=SourceDomain,DC=com was not created on target. Its parent has probably been deleted after migration.
The GUID that needs to be on the matching attribute of the OU (admindisplayname by default) is the GUID of the source OU that matches it. Therefore because the OU exists it will not merge or recreate the OUs. The tool has been configured to migrate OUs will experience a conflict of interest.
Two possible workarounds.
1. Delete existing structure on target OU. This option may not be practical nor possible.
2. Break down the migration sessions to a one to one migration. I.e. OU to OU and migrate as a flat list vs migrating the OU itself.