Crowd - Add LDAP user to local group

[Sandro Gehrig]

We have recently setup crowd to use active directory and authentication works as expected.
But even though the new directory is configured to "Manage groups locally", we cannot add its users to local crowd groups.
If go to the "Groups" tab of a user, it shows the info
"Permission to modify groups has been disabled for this directory."
I have been reading the crowd documentation "Configuring an LDAP Directory Connector" but could not find a reason why this does not work with our configuration. Is there a setting I am missing?

We use Crowd Version 3.1.1

Thanks for any help or suggestions