Sometimes when I save a drawing, the isometric view on the first sheet disappears and it saves that way. This happens about once every two weeks and there's been nothing I or my coworkers can do to fix it. Sometimes it fixes itself after a while but its very sporadic. If I rebuild or CTL-Q the image reappears but as soon as I save it, it disappears again. Does anyone have a fix for this? The picture below is an example of what the drawing is doing.