I don't understand exactly, but an error appears when I select a category from which to choose random questions and I don't click on apply filter. It seems that moodle sets the default category and hence the problem.
I have to be careful to click on "apply filter". It may be a good idea to apply the automatic filter when changing or selecting a question category.
I have to be careful to click on "apply filter". It may be a good idea to apply the automatic filter when changing or selecting a question category.