Thanks Vaselina,
Here are some points regarding your comments:
Orders not appearing in delivery due list
The items in the order are not related to each other in term of BOM. They are all finished products that are sold separately. I am a functional consultant and I should ask a technical consultant regarding any user exits that may be used for this purpose.
Orders blocked for credit
It is also strange that there is no requirement for delivery due list. Maybe the development team somehow wrote some codes in the background to fulfill this requirement. In our IDES system, the requirement that you have mentioned is defined.