Array Sets Quantity Assignment Issue

Summary:

We use Array sets in our models and users added quantity against some of the items in the array to configure the model. When user reconfigure and in a case that one of the item they had already added quantity for has become obsolete (and hence got dropped from the array set), the quantity that was assigned to that item (on a certain index of the array) now get assigned to the next item in the line as that item has now taken the position of the removed item

Our expectation is that the configuration engine should realize that and thrown an error/message but nothing happens and now suddenly a different part shows up in the configuration result unexpectedly. The document below may be help understand the problem better.