User accounts and LDAP

We are running Vibe 3.4 and synchronizing user accounts with LDAP. Under LDAP settings, we have Vibe set to "Delete users that are no longer in LDAP", however, this does not seem to be occurring. I see lot of disabled accounts and a lot of active ones for users who are no longer in the tree. Has anyone else experienced this?

Also is there a manual way to remove accounts added by LDAP? All I can do under the User Accounts tab is enable the accounts, there is no delete option.

Thanks,
Tom