Solved. I was creating datetime from empty field:
new \DateTime(get_field('date', $item->ID, false))
Yes! Thank you very much for de code and the trick.
$foto = get_field('fotopersona', 'personas'.'_'.$term_object->term_id);
Another clue:
var_dump(get_fields($term_object->term_id));
Returns:
/srv/www/soux-calvo.dev/current/web/app/themes/sc/taxonomy-personas.php:10:boolean false
I forget to mention: any attempt to get_field described above returns nothing.