Problems with Shortlink in Facebook etc.

Is there an easy way of updating a WP generated shortlink? Quite often the images available on Facebook don’t match the content of the page – I’ll get horribly pixelated random elements like facebook/twitter ‘share’ buttons rather than the images from the post or page.
My latest page share offered the pixelated share buttons mentioned above and a ‘slugline’ advising ‘page not found’. I may have been a bit quick out of the traps copy/pasting the shortlink to Facebook as the page ‘update’ was loading, but all subsequent attempts to post on Facebook still show the ‘page unavailable’ slugline and random images even though the link works perfectly…
I’ve tried editing the page and resaving etc, but nothing fixes it – the shortlink seems to have the ‘error’ text and dud images permanently attached in some way and i can’t find any way of unattaching them. I don’t really want to delete the page and start over, because doing so will leave the ‘broken’ link from the deleted page still out there, iyswim…