Problems with LDAP and Talk via iOS App

Hello, we use the current version of NC14. The server is freshly installed and everything works so far.
Now we have LDAP and SMB in use. That works too.
Now I have the following problem with the app “Nextcloud Talk” on iOS stated. An AD group is enabled for access in the LDAP configuration. All users appear and can log in with it.
But when I look in the App Talk under contacts, I see all users of the entire domain. So also users who are not in the unlocked group. It also does not do anything to delete the app completely from mobile phone and reinstall. After the new login, all contacts of the entire domain reappear.
The joke is that Talk in the browser only shows the contacts who are really in the group that I unlocked.
I suspect that the contacts are cached somewhere in the database. In other words, if they were in there, they will always be displayed. Regardless of whether the users are still active or already deleted.
Can anybody confirm this?
That’s pretty uncool.
Thank you.

I have the solution:
sudo -u www-data php /var/www/html/occ ldap:show-remnants
sudo -u www-data php /var/www/html/occ user:delete [Nextcloud name]

And config.php
‘ldapUserCleanupInterval’ => 20,