Teamcenter PLMXML Delta Import - import new file into existing dataset

Question

I'm trying to import an ExternalFile (ImanFile) into an existing dataset via plmxml "incremental import" (delta import) on Teamcenter 12.1.

Import does not raise any error/warning but there is a problem:

• The new ImanFile is created but NOT added to the dataset "References"

Also unexpected: you can find the newly created ImanFile using the UID, but NOT with the TC "ImanFile..." query

PLM XML

<PLMXMLDelta xmlns="http://www.plmxml.org/Schemas/PLMXMLSchema" schemaVersion="6" author="unset" time="" date="">
    <!-- the existing dataset in TC -->
    <ExternalReference type="DataSet" id="id6">
        <ApplicationRef application="Teamcenter" label="kTgRkZRHhy1RnD" version="kTgRkZRHhy1RnD"/>
    </ExternalReference>


    <Add id="id0">
        <!-- the new file -->
        <ExternalFile format="CATProduct" locationRef="add/test.CATProduct" id="id8"/>
    </Add>
    
    <Modify attributeName="memberRefs" targetRef="#id6" op="add" valueRefs="#id8"/>

</PLMXMLDelta>

Log

---

   PLMXML Log File Header   
   ----------------------   
            IMPORT          
****************************
Server Hostname :  ...
Teamcenter version :  Teamcenter V12000.1...
Syslog-FileName :  ...
LOG-FileName is:  add.xml.log
XML-FileName is:  add.xml
XSLT-FileName is:  
TransferMode Name :  incremental_import
OverWrite-ExistingData is:  0
CheckOutObjects-UponExport is:  0
CheckFor-ExportPrivilege is:  1
****************************
****************************
XML Element ====>
Processed Element [ExternalReference] Id [#id6]
Imported As ====>
Processed Object [kTgRkZRHhy1RnD] of type [CATProduct]
Error: None
****************************
****************************
XML Element ====>
Processed Element [ExternalFile] Id [#id8]
Imported As ====>
Processed Object [H_hRkZRHhy1RnD] of type [ImanFile]
Error: None
****************************
=====  END OF (DETAILED OBJECT TRANSLATION) ===== 

///// Teamcenter Import Summary BEGIN: Processed the following PLMXML Elements
  Element:: ExternalFile                                       Count:: 1 
  Element:: ExternalReference                                  Count:: 1 
///// Teamcenter Import Summary: Processed the following Teamcenter Objects
 TCObject:: CATProduct                                         Count:: 1 
 TCObject:: ImanFile                                           Count:: 1 
///// Teamcenter Import Summary END: /////