After you manually assign or remove a teacher from a course, the course listing screen does not update the teacher names with your latest changes.
Steps to reproduce this issue:
1. In a course, manually assign the teacher role to a single user
2. Browse the courses (either via expanding categories or a quick search for the course) and take note of who is listed as the teacher of the course. eg. via http://yourmoodle.com/course/index.php
The teacher listed for the course would immediately reflect the manual enrolment just created.
The teacher(s) listed for the course remain unchanged.
A further test is to remove a teacher already manually assigned and check the course listing screen to see that the teacher is still listed for the course.
You can fix this by purging all caches, either via the gui, or command line (/usr/bin/php yourmoodle/admin/cli/purge_caches.php).