Upgrade from One Identity Manager 8.1.5 to 9: LDAP Connector and LDAP Connector (version 2)

soon we will upgrade the One Identity Manager from version 8.1.5 to 9. According to the release notes 8.2.1 (https://support.oneidentity.com/technical-documents/identity-manager/8.2.1/release-notes/3#TOPIC-1805043) the LDAP connector will not be supported in the future and the new LDAP connector (version 2) should be used.
Currently we are using the "old" LDAP connector, which synchronises the AD LDS target system and for our upgrade we can not use this connector anymore.
We tried to create a new synchronization project with the LDAP connector (version 2) but it can not be saved as we get the error message that "the object could not be saved. There is already a LDAPAccount with the name ..." and also we deactivated the "old" project and deleted the "old" base-object.
How can I resolve this error?