Expiration Date in Reservation Entry Table

Hello All,

I have a problem with Item Tracking.
I track items by Lot No. and Expiration Date.
During the Purchase, I put Lot No. and Expiration Date manually and the systems records them in the Item Ledger Entry and this part is ok.
But, when I try to sell this item which has Lot No. and Expiration Date (I retrive the Lot No. and the Expiration Date from ILE in the Item Tracking Lines in the SO), I notice that that in the Reservation Entry table the Lot No. is recorded but the field Expiration Date is empty.
All the sales entries in Item Ledger Entry have expiration date empty. Why is this???
Can anybody help me with this matter?

Tx