I've found some cases in the Designer when working on a Perspective screen and I select a component, the selection highlight is in the wrong place. I think it has to do with the component being inside a container that has been scrolled. I can still click and drag the component to move it, but the preview appears in both places.
Here, I've selected the checkbox and dragged it to the right. You can see the selection is below and even outside the actual screen border:
