Enroling a new teacher on a course is not reflected immediately in the courses category view (/course/index.php?categoryid=??). Clearing the cache updates view immediately.
1. Navigate to a course.
2. Enrol a user as a teacher on the course.
3. Navigate to course's category view - http://moodleurl/course/index.php?category=??
4. Enrolled teacher is not reflected in view.
NB: That if the cron runs whilst carrying out these steps, sometimes the view is updated. Clearing the all caches - Site Admin->Development->Purge all caches does update the category view.
It is possible that some themes may not display teacher information in this view but several do.