Kasim,
It can be because the XML coming from source is not matching to Sender Service Interface.
Solution:-
1. Remove the Operational Mapping from Interface Determination or ICO.
2. Test the interface. Capture the xml coming from source in message monitoring.
3. Compare above xml with your current sender Message Type.
4. Update the sender Message Type.
5. Add the Operational Mapping in Interface Determination or ICO.
6. Test it again.