I have just figured out that changing any field other than replacing the image does activate the SAVE button. For instance, if I cut the link and paste it back in. Until just now i have rarely used the Title and Text, and i have not had to change any of them.
so, the issue of the SAVE button not being activated by making a change ONLY to the image is the issue.
You may or may not consider that a bug. if you do, i guess i would put it near the bottom of the list.