Howard Miller

...you'll need to remove the rewrite rules from your web server as well.

No... but my first thought is that the creation has failed - probably before this. Run with Debugging up full. Find and check your error logs. We're looking for a clue as to what went wrong.

If I remember correctly, the very large test course are HUGE and probably need a lot of resource to run.

Well... let's start with the easiest things. How often are you running cron? Are you checking the task logs for any issues?

This is a symptom of a problem. Not the problem. So, unfortunately, your research about locks is probably irrelevent.

This means that the *previous* operation had failed to complete and was holding the session open. As Moodle does not allow you to have multiple sessions open at the same time, you see this when you try to refresh the page / open a new tab and so on.

The problem is whatever you did *before* this that didn't complete.

There is "similar" and then there is "similar". Please post the details. If it turns out to be unrelated, we can split the discussion.