Fatal error: Uncaught Error: Interface "Nextend\Framework\Form\ContainedInterface" not found in /var/www/andovercg/staging/wp-content/plugins/smart-slider-3/Nextend/Framework/Form/AbstractField.php:12 Stack trace: #0 {main} thrown in /var/www/andovercg/staging/wp-content/plugins/smart-slider-3/Nextend/Framework/Form/AbstractField.php on line 12