Tim Hunt

That is not the right thinking.

When thinking about your code, you need to think about capabilites. What does thing menu let someone do, then in your plugin define a capbility: myplugin:managethingy

Then, it is a configuration matter which roles have that capability - but you can set defaults for that which are used when your plugin is installed.

No problem at all. Shared goemaxima server is a very sensible setup.

If you are using Moodle 4.2 or later, then you can deal with this.

After the settings change you made, go to Quiz resluts -> Grades. Then, but the 'Never submitted' attempts will have a 'Re-open attempt' button in the table. Click it!

Since the time limit is past, when you click it, the attempt will immediately be submitted according to the 'The ongoing attempt is automatically submitted.' setting, and the student will get a grade.

You can select the questions in the list, and then at the bottom there is With selected -> Move to ...

Of course, you need to create the new categories you want to move them into first.

Well, if you cannot reproduce what happened, it is hard to know.

One thing you could do is to look very carefully at the logs (both Moodle logs and web server logs) to see if you can work out what acutally happened here.