We are migrating an old 2.7.20 Moodle to our new 3.6.7 Moodle and are experiencing an issue with a number of courses where (seemingly random) enrolled users are not being created/enrolled onto the destination course restore and their submitted submitted assignments (for those that are enrolled) are not restored.

We have checked the MBZ and the "users.php" has all the users and the MBZ size would suggest that all the submitted assignment files are contained within.

The odd thing we have noticed is that all the users who have "Never" accessed the course have been restored, however none of the students who *have* accessed the course on the source are not enrolled onto the new.

The extra complexity we have is that our old Moodle used LDAP authentication (with usernames such as S12345678 for students and id123456 for staff) however our new Moodle uses OpenID/Office365 (usernames are all email addresses). Many of our users access both platforms. We are a University and rather than upgrade the old Moodle we have created a new Moodle and have the majority of courses on new Moodle, with a subset of legacy courses on old, that we are slowly migrating to new.

We wonder if we are experiencing a well known issue where the source user cannot be created (and thus matched by the restore process for the user data) on the new Moodle because they already have an account with the same email address (but different username) on the new destination?