It appears that in Form.php in the following function
private function enqueue() {
wp_enqueue_style( 'mbfs-form', MBFS_URL . 'assets/form.css', '', MBFS_VER );
wp_enqueue_script( 'mbfs', MBFS_URL . 'assets/frontend-submission.js', array( 'jquery' ), MBFS_VER, true );
$this->localize_data = array_merge( $this->localize_data, [
'ajaxUrl' => admin_url( 'admin-ajax.php' ),
'nonce' => wp_create_nonce( 'ajax_nonce' ),
'ajax' => $this->config['ajax'],
'redirect' => $this->config['redirect'],
'confirm_delete' => __( 'Are you sure to delete this post?', 'mb-frontend-submission' ),
] );
}
'ajax' is always getting set to false, regardless of what the shortcode value is for 'ajax'.