No change of jpg quality of image thumbnails possible

Adding of

add_filter(‘jpeg_quality’, function($arg){return 50;});
add_filter( ‘wp_editor_set_quality’, function($arg){return 50;} );

in functions.php of childtheme did not work.

Using plugins (e.g. Regenerate Thumbnails Advanced or Regenerate Thumbnails) to change the jpg quality also did not work.

Only inserting the lines in functions.php of the theme is OK.

Enfold 4.5.7.1 beta3

Regards
Christian