CentOS 7.9 & FreeIPA problem (CA role can't be added on a replica)

We have a freeipa node configured as replica.

We need to add the CA role.

With ipa-ca-install -d command, we get this error message :

ipapython.ipautil: DEBUG    stderr=
ipalib.install.sysrestore: DEBUG    Loading StateFile from '/var/lib/ipa/sysupgrade/sysupgrade.state'
ipalib.install.sysrestore: DEBUG    Loading StateFile from '/var/lib/ipa/sysupgrade/sysupgrade.state'
ipalib.install.sysrestore: DEBUG    Saving StateFile to '/var/lib/ipa/sysupgrade/sysupgrade.state'
ipalib.install.sysrestore: DEBUG    Loading StateFile from '/var/lib/ipa/sysrestore/sysrestore.state'
ipalib.install.sysrestore: DEBUG    Loading Index file from '/var/lib/ipa/sysrestore/sysrestore.index'
ipaserver.install.service: DEBUG    Configuring certificate server (pki-tomcatd). Estimated time: 3 minutes
Configuring certificate server (pki-tomcatd). Estimated time: 3 minutes
ipaserver.install.service: DEBUG      [1/28]: creating certificate server db
  [1/28]: creating certificate server db
ipaserver.install.service: DEBUG    Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ipaserver/install/service.py", line 567, in start_creation
    run_step(full_msg, method)
  File "/usr/lib/python2.7/site-packages/ipaserver/install/service.py", line 557, in run_step
    method()
  File "/usr/lib/python2.7/site-packages/ipaserver/install/cainstance.py", line 1260, in __create_ds_db
    api.Backend.ldap2.add_entry(entry)
  File "/usr/lib/python2.7/site-packages/ipapython/ipaldap.py", line 1580, in add_entry
    self.conn.add_s(str(entry.dn), list(attrs.items()))
  File "/usr/lib64/python2.7/contextlib.py", line 35, in __exit__
    self.gen.throw(type, value, traceback)
  File "/usr/lib/python2.7/site-packages/ipapython/ipaldap.py", line 1029, in error_handler
    raise errors.DuplicateEntry()
DuplicateEntry: This entry already exists

Any idea about this error ?

FYI, we’ve also tried to install the replica with --setup-ca but we get the same error.

Thanks in advance for your support.

PS : IPA release = 4.6.8-5
Centos release = CentOS Linux release 7.9.2009 (Core)