Sales order number (KDAUF) not updated in MSEG for Mvt 601 because of item category group.

Dear Experts,

I have a problem with updating MSEG-KDAUF during outbound good issue (601).

For materials with an specific item category group (MVKE-MTPOS) the KDAUF will not updated during good issue. Here is MB51 report for a material which has issued two times with different item category but same sales order, movement type and....; but as you see for one of them sales order is bland and the others not.

I have checked the item category groups setting and there is nothing significant.

Any idea?