I don't know if it's happened to you, but every now and then and randomly, the image points I create disappear.
I create a new sprite and set one or more image points and close the window. When I open it again none of the image points I created are there, they disappear.
But it's something that doesn't happen all the time, so I can't reproduce it to register the bug. What I know is that it always happens with new sprites, the ones that were already created don't disappear.