Retrobilling & pricing modifier issues

 Has anyone had any issues with Retrobilling giving back discounts to a customer during Retrobilling when it shouldn't?

We have a particular modifier that is used for quantity price breaks.  Even though we have set up this modifier with Retrobilling turned off for the list line adjustment event phase it is still acknowledging this discount and trying to take it away from the customer?

History:  We originally did not have have an expiration date on the list line adjustment event phase and we were producing a similiar scenario where we were producing Retrobills for customers giving them back their discount that was given via a pricing modifier.  We added the expiration date on the event and then we solved the issue, UNTIL we added this new modifier.