For one of our Sales Orders, when we click Next Bill and try to change the quantity on one of the Item Groups in the Invoice that is creating, we receive the following error:

All members of this group are associated with a wave transaction. The item quantity for each member cannot be decreased below the quantity included in a wave.

This error doesn't make any sense to us because:

• We increased the quantity, not decreased. So that makes it impossible for the error message to be correct.
• We can remove all the items from every group in the Invoice, and it will still throw the error when we change the group quantity. It is not possible for the error message to be correct in this case because there are no group members (whether they belong to a wave or not) any more if we do this.