Duplicate delivery schedule line quantities - 2LIS_12_VASCL

Hello,

We are experiencing and occasional issue and would appreciate any assistance.

The end result is duplicate delivery schedule line quantities. It is caused by the following;

            A sales order is created for a quantity of 1200, it has 2 schedule lines, the 2^nd has the quantity of 1200. A delivery is created but there are only 1100 available on-hand. The delivery is created with 2 schedule lines, the quantity of 1100 is on the 2^nd. At this point BW receives the two schedule lines for the sales order and two for the delivery.    

            The sales order qty is now modified and the 2^nd schedule line is deleted. However, the two delivery schedule lines are not modified. BW receives the delete for the sales order schedule line 2 and the modified schedule line 1, which now contains 1100. No changes are received for the delivery at this point.

          When the delivery is picked BW receives the delta for schedule line 1 with the quantity on it from the sales order. However, there is never a delete for schedule line 2 of the delivery, which would correspond to the sales order change. BW now has the delivery schedule lines 1 and 2 with the quantity of 1100 on each.

          It is our understanding that SAP does not maintain delivery schedule lines and generates them from the sales order schedule lines. In this situation the sales order and delivery are out of sync, but only for BW.

            Any assistance would be appreciated.