Promotional modifier re-applied when updating an order line

Hi everybody. We are facing a strange problem with modifiers in an environment upgraded from 11.5.10.2 to 12.2.9, maybe you can help us with this. We have defined a promotional modifier, so when you enter in the sales order a line for item S1, then the system creates a line for item F1 (an item “for free” linked to S1). If you do the same for S2, it creates a line for item F2 (an item “for free” linked to S2). And the same for S3 (linked to F3) and S4 (linked to F4) ….Everything OK, as defined in the modifier.

But, if you go later to the entered order and update a line for one of the existing ‘S’ item in the order, it creates AGAIN the free lines for F1, F2, F3, F4…No matter the S you updated, it creates lines for every F item linked to each existing S item in the order.