Wayan, what you have observed, that you need to reselect an image to get it into the canvas using those wee buttons;
I tried it, and I think the problem has to do with the sorting of the resources. The default way of sorting is alphabetical a-z. If I add some images in that order, it works, you only select an image once. But if I add images in any other order, the last image alphabetically will be inserted if you don't reselect.
I wonder what would be the best solution here; have a sorting option 'according to sequence' or an option not to sort at all, or what...