CB 2.0.10
Joomla 3.4.3
Under the registration tab in CB configuration I have Ajax Username Checker set to Yes but in the last couple of weeks I have had 2 new members join my site using existing usernames.
This causes problems because their subscription payment (via AEC) gets allocated to the existing user and their own membership doesn't show at all.
Are there any settings elsewhere that I should check or change?