I had the same problem.
I solved the problem by adding the following code in 2 files.
*** function testFocusKw() in file wp-seo-metabox.js ***
Replace the function with this code:
function testFocusKw() {
// Retrieve focus keyword and trim
var focuskw = jQuery.trim( jQuery('#yoast_wpseo_focuskw').val() );
focuskw = focuskw.toLowerCase();
var postname = jQuery('#editable-post-name-full').text();
var url = wpseo_permalink_template.replace('%postname%', postname).replace('https://','');
p = new RegExp("(^|[ \s\n\r\t\.,'\(\"\+;!?:\-])"+focuskw+"($|[ \s\n\r\t.,'\)\"\+!?:;\-])",'gim');
str = focuskw.replace(/\s+/g,"[-_\\\//]");
//CML remove accents from slug
var from = "àá?aèé?êìí??òó??ùúü????à??éèê?ù";
var to = "aaaaeeeeiiiioooouuuuyncAACEEEEU";
for (var i=0, l=from.length ; i<l ; i++) {
str = str.replace(new RegExp(from.charAt(i), 'g'), to.charAt(i));
}
p2 = new RegExp(str,'gim');
if (focuskw != '') {
var html = '<p>Your focus keyword was found in:
';
html += 'Article Heading: ' + ptest( jQuery('#title').val(), p ) + '
';
html += 'Page title: ' + ptest( jQuery('#wpseosnippet .title').text(), p ) + '
';
html += 'Page URL: ' + ptest( url, p2 ) + '
';
html += 'Content: ' + ptest( jQuery('#content').val(), p ) + '
';
html += 'Meta description: ' + ptest( jQuery("#wpseosnippet .desc span.content").text(), p );
html += '</p>';
jQuery('#focuskwresults').html(html);
}
}
*** function score_url() in file class-metabox.php ***
I added this code after the declaration of variable needle
$needle = $this->strip_separators_and_fold( $job["keyword"] );
// Remove Accented UTF-8 Characters
$search = explode(",","?,?,?,á,é,í,ó,ú,à,è,ì,ò,ù,?,?,?,?,ü,?,a,ê,?,?,?,?,e,i,?,u,à,?,?,é,è,ê,?,ù");
$replace = explode(",","c,ae,oe,a,e,i,o,u,a,e,i,o,u,a,e,i,o,u,y,a,e,i,o,u,a,e,i,o,u,A,A,C,E,E,E,E,U");
$needle = str_replace($search, $replace, $needle);