GOT A SOLUTION!
1) Using Editor, open “custom-styles.php”
2) search this line: .content-masonry .entry-title
{ font-size: <?php echo esc_html( (int)$fluida_ftitlessize – 60 ) ?>%; }
3) the problem seems to be the nonsense -60% value of the font. I’ve changed ” – 60 ” with ” – 20″ (after having experimented other values, of course), and now titles seem titles and not footnotes.
Waiting for the official solution.