The "Next lesson" button does not work correctly.

It should always go to the very next incomplete lesson in the current module the customer is in. Instead, if a customer decides to skip a few lessons and jump to a different lesson in the next module, and then go back to the previous module to complete the lessons in that module, the "Next lesson" button will always ignore the incomplete lessons in the current module and skip ahead to the lesson that follows the farthest completed lesson.

This is causing customers to get lost and confused in the courses.

Please fix this.