Course sites created before we introduced 'Course Description' & 'Course Information' add-in parts are missing a required script file. To work around the issue you need to add a Script Editor web part to the page with the mentioned add-in parts. I.e. you'll need to add 3 Script Editor web parts to the page:
Next, edit each web part snippet in the following way:
- enter <div class="lms365-course-description"></div> for Course Description web part
- enter <div class="lms365-course-info"></div> for Course Information web part
- Link to script file is placed in the last script web part, enter
Save the changes. Now the 'Course Description' & 'Course Information' add-in parts that you added to the page should work.