You need to pick the object and in this case you could use Pick nth instance where 0 is the first button, 1 is the second button. This is essentially picking by the object's IID which is the order in which the buttons were created. Currently you are just applying to all button objects.
I try it, and don't work.
Pick nth instance, overlapping point, ....
With or without "wait" (between create and load image).
When I load an image, all instances change it.