Currently I don't have access to the latest CU available for AX 2012 R3. Within R3 RTM there is no standard entity for ReqItemTable. Do you have a CU where it is standard or was the entity created using the wizard?
I suppose you mean with "Target: DMFReqItemTableTargetEntity" the Query used for this entity?
Did you check on the Target entity form if the mapping is really correct? Can you otherwise share some screenshots?