function wpf_course_access_debug( $user_id, $course_id, $access_list = array(), $remove = false ) {

    if ( ! function_exists( 'wpf_log' ) ) {
        return;
    }

    wpf_log( 'notice', $user_id, 'DEBUG User enrolled in course ' . get_the_title( $course_id ) . ': <pre>' . print_r( debug_backtrace( DEBUG_BACKTRACE_IGNORE_ARGS, 50 ), true ) . '</pre>' );

}

add_action( 'learndash_update_course_access', 'wpf_course_access_debug', 10, 4 );