OpenLDAP - how to correct invalid cn values

A bug in a PHP script has caused some entries in the LDAP database to have invalid values:

# James + Bond, people, mi6.gov.uk
dn: cn=James+sn=Bond,ou=people,dc=mi6,dc=gov,dc=uk
sn: Bond
givenName: James
cn:: U3RldmUg
gecos:: U3RldmUg

As you can see, the cn: and gecos: have the invalid values - they should be James Bond.

I did attempt to correct the problem with ldapmodify by putting the following into a file called updateCN.ldif:

dn: cn=James+sn=Bond,ou=people,dc=mi6,dc=gov,dc=uk
changetype:modify
replace: cn
cn: James Bond

and executing the following command:

ldapmodify -x -W -D "cn=admin,dc=mi6,dc=gov,dc=uk" -f updateCN.ldif

This returned the following error

Enter LDAP Password:
modifying entry "cn=James+sn=Bond,ou=people,dc=mi6,dc=gov,dc=uk"
ldap_modify: Naming violation (64)
additional info: value of naming attribute 'cn' is not present in entry

I have also tried ldapmodrdn:

ldapmodrdn -r -f updateCN.ldif

with updateCN.ldif:

dn: cn=James Bond+sn=Bond,ou=people,dc=mi6,dc=gov,dc=uk

cn=James Bond

$ ldapmodrdn -r -f updateCN.ldif

SASL/DIGEST-MD5 authentication started

Please enter your password:

ldap_sasl_interactive_bind_s: Internal (implementation specific) error (80)

additional info: SASL(-13): user not found: no secret in database

and

ldapmodify -f updateCN.ldif

with updateCN.ldif:

dn: cn=James Bond+sn=Bond,ou=people,dc=mi6,dc=gov,dc=uk

changetype: modrdn

newrdn: cn=James Bond

deleteoldrdn: 1

$ ldapmodify -f updateCN.ldif

SASL/DIGEST-MD5 authentication started

Please enter your password:

ldap_sasl_interactive_bind_s: Internal (implementation specific) error (80)

additional info: SASL(-13): user not found: no secret in database

How can I correct the invalid values in the LDAP database?

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