Reservations going aways after partial shipments - is this normal for DJ/SO reservatoins ?

 I am not sure if this an  Inventory  or  WIP  or  OM  problem but I figured I would ask this community if they have any insight since I have gotten good answers in the past -- there does not seem to be a community for  WIP/Discrete MFG.

We are having a problem with  DJ / SO linkages going away after partial shipments. 

Simple example:    We have a sales order line for lets say QTY = 10.    We create a WIP DJ for that item of QTY = 10.    Lets say we complete 6 of the 10  parts on the DJ.     At that point we have 6 inventory reservations to that SO line and 4 Job reservations to that line.     If we ship confirm the partial line quantity of 6  after the ship confirmation the  DJ / SO  link for the remaining quantity of 4  is gone.