Hi

as you know, each question category can have a parent, and this parent is freely assignable. This works fine in all cases except the following:

FULL STEPS

1. In https://yourmoodle.com/question/bank/managecategories/category.php?courseid=1 , create a new question category with a name you'll remember
2. see it visually appear
3. click on the gear icon to get to its settings
4. in the "parent category" dropdown menu, select itself and click "save changes"

WHAT YOU EXPECTED

• Display a error message because a question category cannot be its own parent

WHAT ACTUALLY HAPPENS

• the question category gets saved with no error message, and on the overview screen, it no longer appears. But it's still in the db (we checked).

Since this bug has been around for a while, any fix should include a DB upgrade step to break any category loops (by chaning the parest to the default category to the context, or similar.)

There is a related problem, but moving quesitons when a category is deleted, in this forum thread: https://moodle.org/mod/forum/discuss.php?d=451675