One of our post titles has a quotation mark in it. WordPress is storing the quotation as ’, which is fine for html output, but not so good to pass to rawurlencode, so, on (my) line 90 of public.php, inside pib_button_base, I wrapped $description a bit more.
'&description=' . rawurlencode( wp_strip_all_tags( $description ) );
'&description=' . rawurlencode( html_entity_decode( wp_strip_all_tags( $description ) ) );
I request this to be implemented for future versions.