Backup and restore

After backup/restore to different courses, I received this message "error/AJAX.... " when trying to delete a question from an activity (quiz). Note that I also tried to move the question to a different category: from within the activity and from the question bank. In both cases, Moodle seemed to allow me to do this but I suspect that it didn't really happen. Anyway, I "solved" the problem by duplicating the activity. This seems to delete the unwanted/ghost questions.====== IMHO, (no offense intended) Moodle's question bank has serious issues. I reckon that a possible solution would be to indicate on screen a question's specific ID number. This at least would make plain that two questions - seemingly the same to a user - are in fact in Moodle two different objects/thingees.