Tim Hunt

In the database, look at all the question_category rows for this contextid, and how they related to each other through the .parent links. That should define a tree structure. Seems like you have a cycle, which should be impossible.

If you can, try setting Debugging to DEVELOPER level temporarily, to see if some error is happening. Alternatively, ask your Moodle admin to check the server logs.

The but report where this is being worked on is MDL-85510.

You will get a 'Quiz attempt updated' even every time the use moves from one page of the quiz to the next (or to the attempt summary page). A change will only be recorded in the response history for a particular question if the user made any change to their response to that question.

So, there is nothing suspicious in that log.

Well, whether a query taking 1 second is good or bad depends on the query.

If this is a bug complex report, that is probalby expected. For other queries it would be bad.

You have to look on a case-by-case basis. Find the query in the code, understand what is going on, then use Explain to work out if there are obvious ways to improve it. Then follow Moodle development processes to contribute any improvements.