We are not fortune tellers with a glass bowl.
For a serious analysis a SAP expert would need basic information about the program that is used in this batch job and the basis from where it should take the values.
As I never heard about such a program which generates SLED - in SAP the shelf life expiration date is entered with the goods receipt - I believe this is a homemade ABAP, and nobody here can tell you why your own ABAP does weird things if you do not show this ABAP