I'm on 1.7.3 and running linux with xorg, When I take a big screenshot (either whole desktop or a big enough window) ksnip will capture it all, however, due to ui elements the preview of the image won't show all at once, instead you get scrollbars to see the rest of the image. What I noticed is that when you click save on ksnip, only the part of the image that is currently visible will actually be saved, in other words, what was captured but not currently visible somehow gets cropped out.

Simply taking a full screenshot and clicking save without doing any sort of modifications whatsoever displays this behavior for me.

Edit: The problem also happens if you open an image and then use "save as", again no need to edit the image at all for this to happen.