1. Backup a course with some user data
2. Untick 'include users'
3. Proceed to next page and see you can't select user data
4. Go back to previous step
5. Tick 'include users'
6. Proceed to next page

Expected result:

1. You can continue now users are included

Actual result:

1. You can't

NOTE: I discovered this while testing some code with new dependencies, so its something to do with the dependency management. Also seems that the reverse isn't true. Its only when its 0