I'm not sure I can help with this specifically, but from what you've written here it sounds similar to problems I have at times when trying to change materials for leaves, that is, that the moment after I close the tab and go back to check it, it has either reverted or chosen another material already present in the scene and used it.  Also when changing the scale of objects in ecosystems I find that I need to change them several times before they actually stay as I want them.  Perhaps try doing the operation a couple of times and see if it works that way.