sales-order picking project item proplem

1:In production environment,one sales-order exist an order-line,its item is ITEM1，its project-number is A.Pegging in "MPS/MRP planning" of ITEM1 is "HARD PEGGING" .While picking,system would match ITEM1 those project-number is A,ITEM1 those project-number is null or not A would not match.
2:In test environment,whiling picking,system can match items those prject-number is null as well in most cases.
3:But system can match items those project-number is different from A in another test environment sometimes.
So I just not know what different set up could bring the three cases.