Nextcloud version (eg, 10.0.2): 12 b 2
Operating system and version (eg, Ubuntu 16.04): Ubuntu 16.04
Apache or nginx version (eg, Apache 2.4.25): Apache 2.4
PHP version (eg, 5.6): 7
Is this the first time you’ve seen this error?: Yes
Can you reliably replicate it? (If so, please outline steps): Yes
The issue you are facing: Add user in circle, delete user in Admininterface
User still in circlelist.
I think that’s an issue, if people have someone in their cicles, then a user gets deleted, a new person gets the same username and got stuff shared which may not his business.