Duplicate Accounts (Joomla / Moodle Sync)

Hi, I'm hoping that somebody can help shed some light on a problem I have with duplicate accounts. I found approx. 15 duplicate accounts spread throughout the two years the website has been running.
I have fixed the majority of the accounts by deleting the newest account and then using Joomdles sync feature to re-sync the original account.
Obviously this isn't ideal as any work the user completed on the new account will have been deleted.

To help illustrate this I have included a few screen shots showing an example across joomla, joomdle (plugin) and moodle.







Any ideas of what might be causing this?

Andy

Hi.

I never saw anyone reporting something similar. Do you have any custom way of adding users?
Joomla and Moodle should not let you create new accounts with the same email, so I don't know how this can happen. What I see is usernames are different, so I guess new accounts were created later with a different username.... but how? In normal Joomla/Moodle registrations, it won't let you create account with same email.