I switched default themes, still the same problem.
I also tried deactivating the other plugins and still the same problem.
I had a look at the fatal error on line 88 from the customize.php file but I am not sure how to fix it.
if ( $wp_customize->is_theme_active() ) {
$document_title_tmpl = _x( 'Customize: %s', 'Placeholder is the document title from the preview' );