Fix “wp_register_script was called incorrectly” issue

From an online tutorial I have made a plugin that puts a read me later button at the end of each post which saves the post ID to the userMeta table. It works, but throws an error:

wp_register_script was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks

I have isolated my new plugin as the cause of this problem and tried with different themes. I have searched on this and found that the usual solution is to wrap all scripts and styles in a function and hook that function to the target enqueue action. But that’s what this code does (isn’t it?) and the error is persisting.

Here’s the code:

define( 'RML_DIR', plugin_dir_path( __FILE__ ) );
require( RML_DIR.'widget.php' );

class ReadMeLater {
    /**
     * Action hooks
     */
    public function rml_run() {

        // Enqueue plugin styles and scripts
        add_action( 'plugins_loaded', array( $this, 'rml_scripts' ) );
        add_action( 'plugins_loaded', array( $this, 'rml_styles' ) );

        // Setup filter hook to show Read Me Later link
        add_filter( 'the_excerpt', array( $this, 'rml_button' ) );
        add_filter( 'the_content', array( $this, 'rml_button' ) );

        // Setup Ajax action hook
        add_action( 'wp_ajax_read_me_later', array( $this, 'read_me_later' ) );

    } 

    /**
     * Register plugin styles and scripts
     */
    public function register_rml_scripts() {
        wp_register_script( 'rml-script', plugins_url( 'js/read-me-later.js', __FILE__ ), array('jquery'), null, true );
        wp_register_style( 'rml-style', plugin_dir_url( __FILE__ ) .'css/read-me-later.css' );
    }

    /**
     * Enqueues plugin-specific scripts.
     */
    public function rml_scripts() {        
        wp_enqueue_script( 'rml-script' );
        wp_localize_script( 'rml-script', 'rml_obj', array( 
            'ajax_url' => admin_url('admin-ajax.php'),
            'check_nonce' => wp_create_nonce('rml-nonce')
        ) );
    }

    /**
     * Enqueues plugin-specific styles.
     */
    public function rml_styles() {         
        wp_enqueue_style( 'rml-style' ); 
    } 

    /**
     * Adds a read me later button at the bottom of each post excerpt that allows logged in users
     * to save those posts in their read me later list.
     *
     * @param string $content
     * @return string
     */
    public function rml_button( $content ) {

        // Show read me later link only when user is logged in
        if ( is_user_logged_in() && get_post_type() == post ) {
            $html .= '<a href="#" class="rml_bttn" data-id="' . get_the_id() . '">Read Me Later</a>';
            $content .= $html;
        }
        return $content;

    } 

    /**
     * Hook into wp_ajax_ to save post ids, then display those posts using get_posts() function
     *
     * @access public
     * @return mixed
     */
    public function read_me_later() {

        check_ajax_referer( 'rml-nonce', 'security' );
        $rml_post_id = $_POST['post_id']; 
        $echo = array();
        $new_word =$_POST['new_word'];

        global $wpdb;
        global $tefl_db_version;

        $table_name = $wpdb->prefix . 'userWordsNew';

        $charset_collate = $wpdb->get_charset_collate();

        $sql = "CREATE TABLE $table_name (
            id mediumint(9) NOT NULL AUTO_INCREMENT,
            time datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
            name tinytext NOT NULL,
            text text NOT NULL,
            url varchar(55) DEFAULT '' NOT NULL,
            PRIMARY KEY  (id)
        ) $charset_collate;";
            require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
        dbDelta( $sql );

        add_option( 'tefl_db_version', $tefl_db_version );

        /* add data */
        global $wpdb;
        global $current_user;
        wp_get_current_user();

        if ( is_user_logged_in() ) { 
            $thisUser = $current_user->user_login;
        }
        else {
            wp_loginout();
        }

        $student_name = $thisUser;
        $myWord_text = $new_word;

        $table_name = $wpdb->prefix . 'userWordsNew';

        $wpdb->insert( 
            $table_name, 
            array( 
                'time' => current_time( 'mysql' ), 
                'name' => $student_name, 
                'text' => $myWord_text, 
            ) 
        );

        if ( get_user_meta( wp_get_current_user()->ID, 'rml_post_ids', true ) !== null ) {
            $value = get_user_meta( wp_get_current_user()->ID, 'rml_post_ids', true );
        }

        if ( $value ) {
            $echo = $value;
            array_push( $echo, $rml_post_id );
        }
        else {
            $echo = array( $rml_post_id );
        }

        update_user_meta( wp_get_current_user()->ID, 'rml_post_ids', $echo );
        $ids = get_user_meta( wp_get_current_user()->ID, 'rml_post_ids', true );

        function limit_words($string, $word_limit) {
            $words = explode(' ', $string);
            return implode(' ', array_slice($words, 0, $word_limit));
        }

        // Query read me later posts
        $args = array( 
            'post_type' => 'post',
            'orderby' => 'DESC', 
            'posts_per_page' => -1, 
            'numberposts' => -1,
            'post__in' => $ids
        );

        $rmlposts = get_posts( $args );
        if ( $ids ) :
            global $post;
            foreach ( $rmlposts as $post ) :
                setup_postdata( $post );
                $img = wp_get_attachment_image_src( get_post_thumbnail_id() );
                ?>
                <div class="rml_posts">                 
                    <div class="rml_post_content">
                        <h5><a href="<?php echo get_the_permalink(); ?>"><?php the_title(); ?></a></h5>
                        <p><?php echo limit_words(get_the_excerpt(), '20'); ?></p>
                    </div>
                    <img src="<?php echo $img[0]; ?>" alt="<?php echo get_the_title(); ?>" class="rml_img">                 
                </div>
            <?php 
            endforeach; 
            wp_reset_postdata();
        endif;

        // Always die in functions echoing Ajax content
        die();

    }
}
$rml = new ReadMeLater();
$rml->register_rml_scripts();
$rml->rml_run();

Many thanks for any suggestions on how I can clear this error!