Mapping Error - IDoc

I get the following runtime exception in XI Monitor when mapping flat file data to ORDERS05 IDoc.

<b>RuntimeException in Message-Mapping transformation: Cannot produce target element /ORDERS05. Check xml instance is valid for source xsd and target-field mapping fulfills requirements of target xsd at com.sap.aii.mappingtool.tf3.AMappingProgram.start</b>

I've checked the following so far:

1) Succesfully tested the test data instance in Design.

2) Disabled the EDI_DC40 segment

3) Verified the sender and receiver agreements

4) Verified the data against the XSDs

Is there anything else I can check that indicates what is wrong?