I need to duplicate a course with all enrolled teachers and students together with graded Workshop assignments in order to do some testing.

1. On production moodle 2.3.4+ system create a course backup in the normal way (as 'Moodle Tsar' system admin) which includes student grades (but not logs). Backup completes without error.
2. expanding the mbz file reveals that all the enrollments are correctly recorded in course/enrolments.xml
3. On the sandbox moodle site (which has exactly the same code — the production site is simply a copy of this) do the full course restore.
4. Open the course and check Course administration > Users > Enrolled users. Only manually enrolled user accounts have been restored.

LMB version :
$plugin->version = 2012091203;
$plugin->release = "2.1.9";

What I expected to happen was that the course be restored with all LMB user enrollments intact and all the grades present.