wp_title() returns ‘page not found’ on page 2

Seems like the title was fetched before the query, and therefore didn’t fetch the custom posts. Had to add a pre_get_posts to my functions.php to make it work:

add_filter( 'pre_get_posts', 'my_get_posts' );

function my_get_posts( $query ) {

    if ( is_home() && $query->is_main_query() )
        $query->set( 'post_type', array('theory', 'tasks', 'tutorials', 'video', 'interactive') );

    return $query;
}