The code below allow for Themeco - X Theme to be integrated with Sensei.

x-theme-functions.php

/**
 * Declare that your theme now supports Sensei
 */
add_action( 'after_setup_theme', 'sensei_support' );
function sensei_support() {
    add_theme_support( 'sensei' );
}

/**
 * Remove the default Sensei wrappers
 */
global $woothemes_sensei;
remove_action( 'sensei_before_main_content', array( $woothemes_sensei->frontend, 'sensei_output_content_wrapper' ), 10 );
remove_action( 'sensei_after_main_content', array( $woothemes_sensei->frontend, 'sensei_output_content_wrapper_end' ), 10 );

/**
 * Add X Theme by Themeco specific custom  Sensei content  wrappers
 */
add_action('sensei_before_main_content', 'x_theme_sensei_wrapper_start', 10);
add_action('sensei_after_main_content', 'x_theme_sensei_wrapper_end', 10);

function x_theme_sensei_wrapper_start() {
        if ( is_singular( 'course' ) ){
            remove_action( 'woocommerce_before_single_product', 'x_woocommerce_before_single_product', 10 );
            remove_action( 'woocommerce_after_single_product', 'x_woocommerce_after_single_product', 10 );
        }
        echo '<div class="x-container max width offset">'.
            '<div class="x-main left" role="main">'
             .'<div class="entry-wrap"> ';
}

function x_theme_sensei_wrapper_end() {

        echo ' </div> <!-- .entry-wrap -->'
             . '</div> <!-- end sensei .x-main left-->';
        get_sidebar();
        echo'</div> <!-- end sensei x-container-fluid -->';
}

/**
 * remove default sensei titles
 */
remove_action( 'sensei_course_single_title', array( $woothemes_sensei->frontend , 'sensei_single_title' ), 10 );
remove_action( 'sensei_lesson_single_title', array( $woothemes_sensei->frontend , 'sensei_single_title' ), 10 );
remove_action( 'sensei_quiz_single_title', array( $woothemes_sensei->frontend, 'sensei_single_title' ), 10 );
remove_action( 'sensei_message_single_title', array( $woothemes_sensei->frontend, 'sensei_single_title' ), 10 );


/**
 * Add custom theme title:
 */
add_action( 'sensei_course_single_title', 'x_theme_sensei_single_title', 10 );
add_action( 'sensei_lesson_single_title', 'x_theme_sensei_single_title', 10 );
add_action( 'sensei_quiz_single_title', 'x_theme_sensei_single_title', 10 );
add_action( 'sensei_message_single_title', 'x_theme_sensei_single_title' , 10 );

function x_theme_sensei_single_title() {
    global $post;

    if( is_singular( 'sensei_message' ) ) {
        $content_post_id = get_post_meta( $post->ID, '_post', true );
        if( $content_post_id ) {
            $title = sprintf( __( 'Re: %1$s', 'woothemes-sensei' ), '<a href="' . get_permalink( $content_post_id ) . '">' . get_the_title( $content_post_id ) . '</a>' );
        } else {
            $title = get_the_title( $post->ID );
        }
    } else {
        $title = get_the_title();
    }
    ?>

    <header class="entry-header">
        <h1 class="entry-title">
                <?php echo $title;?>
        </h1>
    </header>
    <?php
}

It outputs 2 headers (h1's) on single course page.

@bigfootybets the reason is sensei has updated its hooks. Hooks mentioned above are deprecated now.