Figured it out. Needed to reset at facebook’s end. In addition changing components/com_k2/views/item/view.html.php as follows makes facebook show correct image:
// Load Facebook meta tag for item image
$facebookImage = ‘image’.$params->get(‘facebookImage’,’Small’);
$document->setMetaData(‘image’,substr(JURI::root(),0,-1).str_replace(JURI::root(true),”,$item->$facebookImage));
to
// Load Facebook meta tag for item image
$facebookImage = ‘og:image’.$params->get(‘facebookImage’,’Small’);
$document->setMetaData(‘image’,substr(JURI::root(),0,-1).str_replace(JURI::root(true),”,$item->$facebookImage));