Order repricing (order group) with free goods : both adjustment line non stock AND free goods are ge

I'm using A73PC11.

I want to obtain a free good based on a total order quantity. No problem to setup the item branch plant nor the dedicated adjustment. I have different quantity of free goords depending on the order quantity. Everything is correct except in the sales order entry, I obtain both the free goods line with the correct quantity and the non stock line type too.

In fact, after many attempst, I discoverd that if you put the basis code equal to '2' (F472/ADBSCD='2'), you obtain both lines. If you put any other value then you obtain only the wished free good line despite the fact there is no link between the price (base or current net price) for this kind of adjustment.