MPN number inherited in Planned Order even if not maintained in Source List

[lmoc]

Hi Gurus,

Hope someone may help me. We have three materials wherein if MRP is run for them via MD03, the planned orders created get the MPN number (the HERS material number) although the MPN number is not maintained in the Source List. Please see the screenshot wherein the MPN number is reflected. Moreover, when we try to change the Planned Order and click the Assign button, the MPN number field disappears. Has anyone experienced this? What might be causing this? Thank you.

  

PLM Enterprise Asset Management (EAM)/Plant Maintenance (PM) SAP S/4HANA