GraphComparator could not find the new member of ArrayList

Start by reproducing the provided ArrayList example and inspect GraphComparator.compare with the supplied getIdFetcher in both argument orders. The work is done when the reverse comparison reports the element added to the list, while preserving the existing OBJECT_ORPHAN behavior.

I am having a problem while using your great library as I want to compare two ArrayLists for differences using GraphComparator. I deleted an element of one of the lists and when I compared the old list and new list it shows that there is OBJECT_ORPHAN command. But when I reversed it by comparing the new list and the old list, it should show that there is a new object but somehow it could not detect.

My code is like this:

List<UnifiedBucket> ubs= new ArrayList<>(); // Assume I already put elements in the list 
List<UnifiedBucket> ubsCopy = cloner.deepClone(ubs);
ubsCopy.remove(25);
ubsCopy.get(14).setRawPolicy(null);
List<GraphComparator.Delta> deltas = GraphComparator.compare(ubs, ubsCopy, getIdFetcher()); //This works fine as I could find the OBJECT_ORPHAN

for (GraphComparator.Delta delta : deltas) {
	if (delta.getCmd() != GraphComparator.Delta.Command.LIST_SET_ELEMENT) {
		System.out.println(delta);
	}
}

List<GraphComparator.Delta> deltas2 = GraphComparator.compare(ubsCopy, ubs, getIdFetcher()); //This does not work fine as I could not find the new element that is not deleted in the ubs list

for (GraphComparator.Delta delta : deltas2) {
	if (delta.getCmd() != GraphComparator.Delta.Command.LIST_SET_ELEMENT) {
		System.out.println(delta);
	}
}

Any reason why?