Error while executing write to data store entity from Interface

Hello,

I am getting below error when i was trying to write to execute smart service write to data store entity from interface.

Few points about CDT and Table:-

1. CDT is nested 
2. valueMultiListValue this column is present in cdt(DDP_QuestionResponse) but not present in database but still i can retrieve data into it.
3. When i try to insert data into database table(DDP_QuestionResponse) from process model by creating type of cdt it works as expected.
   
   
4. When i try to insert data from valueMultiListValue  column data it will add data to other table which is expected.
5. NO trigger applied on table.

Error i am getting on Interface:-

Interface Definition: Expression evaluation error: An error occurred while executing a smart service: An error occurred while trying to write to the entity “DDP_QuestionResponse” [id=3dc6d3fc-8a9e-4bcc-b781-112d22727019@1850, type=DDP_QuestionResponse (id=3860)] (data store: DDP Data Store). Details: org.hibernate.PropertyValueException: not-null property references a null or transient value:

CDT and XSD structure of Column valueMultiListValue  :-

 <xsd:element maxOccurs="unbounded" minOccurs="0" name="valueMultiListValue" nillable="true" type="xsd:int" />

Questions :-
How do i write data to table from interface?
How database write working as expected from process model?

If CDT column is transient how do i able to write it to other table from valueMultiListValue column value?