Hi,
I was also having trouble with the Tutor LMS free version 3.9.5. I wanted to change the course author, and after selecting a new author and saving, it would list both old and new users on the course page. I could not see any way of fixing this from the UI. I managed to fix it from the database though. To show all the authors for the course, you can run the following query:
SELECT * FROM wp_usermeta WHERE meta_key LIKE '_tutor_instructor_course_id' AND meta_value LIKE <your_course_id>;
This will list all the authors for a course. The user_id column would be the post author ID. You can then remove all entries but one.
Hope this helps!
