Joined document insert via API - problem -please help

I dont know if this is fixed in 3.* version but i had a serious problem with inserting joined document via API.
Here is the report

This is the document to be insert. The referenced document does exist.Inserting via Tamino Interactive Interface works fine.This is document joined via ino:key with other existing document.

<?xml version='1.0' encoding='UTF-8'?>
<wykazTr NipIO=‘5248561347’ lKart=‘1’ pDat=‘2000112’ pCzas='212519’
podpisE=‘083dvs823aj637g8i30yq0e’>


280
0
20000101
7467755081


0331
0

0
8401522
2000513
ruawlxbgpoq
4326105
PLN
4326105
PLN


<D_ob_id>1
<---- the problem accures here with means its smt wrong with inserting the joined doc via Tamino API
</D_ob_id>


<W_ob_id>2

</W_ob_id>


<B_ob_id>3

</B_ob_id>


52333703845816685632175132282184276
84888608873453121128456486035353223



------------------
Error:
com.softwareag.tamino.db.api.accessor.TInsertException
Access Failure:
ReturnValue:8751
Code:INOXPE8751

HERE
=======
MessageText:Storing an object of this mapping type is not permitted
====
MessageLine:Line 2, Column 534: Storing an object of this mapping type is
not permitted
at
com.softwareag.tamino.db.api.accessor.TAccessFailureVerifier.verifyInsertRes
ponse(TAccessFailureVerifier.java:40)
at
com.softwareag.tamino.db.api.accessor.TXMLObjectAccessorImpl.insert(TXMLObje
ctAccessorImpl.java:93)
at pl.softwareag.pilots.utils.Utils.insertDocumentFromString(Utils.java:55)
----------------------------------------------------------------
Here is the Java method used to do the insert:
Metoda:
public void insertDocumentFromString(String xml,TXMLObjectAccessor database)
throws Exception
{
StringReader stringReader = new StringReader( xml );
TXMLObject xmlObject = TXMLObject.newInstance(
TDOMObjectModel.getInstance() );
xmlObject.readFrom( stringReader );
database.insert(xmlObject); <--------- ERROR HERE!!!
}