Ok, that explains it. You can edit wppa-boxes.html, line 1085:
// The share url
if ( wppa( 'in_widget' ) ) {
if ( wppa_opt( 'wppa_widget_sm_linktype' ) == 'home' ) {
$share_url = home_url();
}
else {
$share_url = get_permalink( wppa_get_the_landing_page( 'wppa_widget_sm_linkpage', __a( 'Social media landing page' ) ) );
$alb = wppa_get_photo_item( $id, 'album' );
$share_url .= '?wppa-album='.$alb.'&wppa-photo='.$id.'&wppa-cover=0&wppa-occur=1';
if ( wppa_switch( 'wppa_share_single_image' ) ) {
$share_url .= '&wppa-single=1';
}
}
}
In the line:
$share_url .= '?wppa-album='.$alb.'&wppa-photo='.$id.'&wppa-cover=0&wppa-occur=1';
you can change wppa-occur=1
into wppa-occur=2
that will fix it.
I will think about a definite solution.
BTW: I inspected the page source and it said it was created by a cache program.
If you de-activate caching: also empty the cache!