Hi, I am trying to create a drawing that is publishable as part of a project, usually, this is no problem, I open a sheet view, create a viewport and then select in model view the area I want to feature within the viewport, however today It appears that whenever I move the image half of it vanishes as I move it, like covering half the drawing with a piece of paper. Is this a setting error that I have or do I have to reinstall the application?