by Colin Fraser.
Hi Leon, there should not be any issue there. It should restore User data and materials without even a blink, whether the Users in the backup are in the system or not.
Having said that, are you checking the backup/restore logs? IS there any sort of error message there? That would be the first place to start I imagine. Is there an issue with "duplicate email addresses"? ie, is the restore process trying to add existing users in a second time as new users? No idea why it would do such a thing, or how, but I suspect it is possible.