Wallpaper move & size

When I try to move and scale a photo for setting as wallpaper the set button does not work. I move the photo and pinch to scale down. The photo moves and scales down but as soon as I release it, it goes back to the orginal size and the set button does not work. If I do not try to move and rescale the set button works fine and sets the photo as wallpaper. Any suggestions on how to move and scale the photo?
Thanks in advance.