I have some courses that fail backup. I think it might be because they imported the course from a different version of Moodle or some other user error but I think it should be prevented. I end up with entries in the mdl_course_sections table that don't correspond to existing resources. They show up in the course as a module logo with no title. The resource can't be deleted because it doesn't actually exist. So the only way to get rid of it is manually from the database.

This problem doesn't cause the backup to fail...but another problem in the database does. I search the mdl_course_modules table for instanceid=0 and I get 1 record for that course. I have to delete this record before the backup will work again.

1. What is causing this database issue.

2. Should there be some kind of resource validation before a link is created or a resource is imported?