Lessons duplication in View

All the lessons in my courses are duplicated in the "lesson" view. e.g. Lesson 1. description - start lesson Lesson 1 description - start lesson Lesson 2 description - start lesson Lesson 2 description - start lesson etc... I am using the latest release 1.15 I did not make any drupal config changes. Duplication is seen as admin and as student. [https://dl.dropboxusercontent.com/u/16709565/lesson-view.jpg ] Any idea what it could be? thanks.