The problem is that the title of the category is used as class for the item element.
Hence the class selector .Class-Name doesn't work due to the spaces (example (°.Bla Bla°)).
My solution i sto add this line
value=value.replace(/ /g,".")
in templates/jf_creativia/html/com_k2/jf_creativia/category.php
// make option object dynamically, i.e. { filter: '.my-filter-class' }
var options = {},
key = $optionSet.attr('data-option-key'),
value = $this.attr('data-option-value');
// parse 'false' as false boolean
value = value === 'false' ? false : value;
value=value.replace(/ /g,".")
options[ key ] = value;
if ( key === 'layoutMode' && typeof changeLayoutMode === 'function' ) {
// changes in layout modes need extra logic
changeLayoutMode( $this, options )
} else {
// otherwise, apply new options
console.log(options);
$container.isotope( options );
}