V_V2 vs. VA02 availability check

Hi, we have a strange problem. When the sales order is created or changed, the availability check brings delivery proposal with multiple schedule lines ( for example around 10 confirmed schedule lines that makes up the order qty and we save this delivery proposal. When we run the hourly V_V2 batch job (or V_v2 in the foreground), the sales order item is confirmed with one schedule line taking the last schedule line date of previous delivery proposal. Ideally these VA02 availibility check and V_V2 should behave the same way. We don't use any delivery priority or anything. Not sure why this is happening. V_V2 should have the same delivery proposal, correct? Because of this weird behaiour, the V_V2 confirmed schedule line is far in the future so this would never come up for delivery due batch job though customer wants partial dliveries (not complete delivery and we don't maintain the completely delivery indicators at all). can you guys help..

We use SAP std availability check 02 with the cumuation option 3 which is SAP recommended.