more info is needed ur requirement and description to the problem is not clear...!
what is the code behind the stacked u used to display ?
which trigger ?
have u created it on a tab canvas or content canvas?
did change any of the stacked property regarding x&y view port or position
and how in relation to your main canvas size & position ?
because setting the width or height of the stacked view port view must be smaller then the main canvas
and how did u set it programatically or through the mouse on the layout?