LDAP Import does not remove the last member in a Group when all the members are removed from a group on the LDAP Server and on the Staging table the member string for the group is empty.

This is controlled by the property "glide.ldap.allow_empty_group"

To fix the issue add the following property in sys_properties and set it's value to true:
Name: glide.ldap.allow_empty_group
type: true/false
value: true