Solution : https://service.sap.com/sap/support/notes/509898 (SAP Service marketplace login required)
Summary : 
      
Key words : 
sap-designed bapi table extensions, symptom transfer errors occur, bapi table extension concept, bapi customer enhancement concept, sap-designed processing, bapi table extension, customer exits / badis, additional mapping step, actual data type, data record x1
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