Description of problem:

The healthcheck tool is reporting an error message while the suffix is indeed correctly defined.
Adding and searching entries work just fine.

$ dsctl <INSTANCE> healthcheck
...

[1] DS Lint Error: DSBLE0001
--------------------------------------------------------------------------------
Severity: MEDIUM
Check: backends:uppercase:mappingtree
Affects:
 -- uppercase

Details:
-----------
This backend may be missing the correct mapping tree references. Mapping Trees allow
the directory server to determine which backend an operation is routed to in the
abscence of other information. This is extremely important for correct functioning
of LDAP ADD for example.

...
$

Version-Release number of selected component (if applicable):

$ cat /etc/redhat-release 
Red Hat Enterprise Linux release 8.7 (Ootpa)
$
$ rpm -qa | grep 389-ds
389-ds-base-1.4.3.31-11.module+el8dsrv+17815+4f95348d.x86_64
cockpit-389-ds-1.4.3.31-11.module+el8dsrv+17815+4f95348d.noarch
389-ds-base-legacy-tools-1.4.3.31-11.module+el8dsrv+17815+4f95348d.x86_64
389-ds-base-libs-1.4.3.31-11.module+el8dsrv+17815+4f95348d.x86_64
$

How reproducible:
Always.

Steps to Reproduce:

1. Define a suffix using mixed cases or upper case for the "nsslapd-backend" and "nsslapd-directory".
For instance:
==============================================
dn: cn=O\3DUPPERCASE,cn=mapping tree,cn=config
objectClass: top
objectClass: extensibleObject
objectClass: nsMappingTree
cn: O=UPPERCASE
cn: O\=UPPERCASE
nsslapd-state: referral on update
nsslapd-backend: UPPERCASE
creatorsName: cn=Directory Manager
modifiersName: cn=server,cn=plugins,cn=config
createTimestamp: 20230603080224Z
modifyTimestamp: 20230603081059Z
nsslapd-referral: ldap://<SUPPLIER_HOST>:<SUPPLIER_PORT>/o%3Duppercase
numSubordinates: 1
==============================================

==============================================
dn: cn=UPPERCASE,cn=ldbm database,cn=plugins,cn=config
objectClass: top
objectClass: extensibleObject
objectClass: nsBackendInstance
cn: UPPERCASE
creatorsName: cn=Directory Manager
modifiersName: cn=Directory Manager
createTimestamp: 20230603080224Z
modifyTimestamp: 20230603080224Z
nsslapd-suffix: O=UPPERCASE
nsslapd-cachesize: -1
nsslapd-cachememsize: 603979776
nsslapd-readonly: off
nsslapd-require-index: off
nsslapd-require-internalop-index: off
nsslapd-dncachememsize: 67108864
nsslapd-directory: /var/lib/dirsrv/slapd-<INSTANCE>/db/UPPERCASE
numSubordinates: 4
==============================================

The trigger seems to be the presence of the "nsslapd-referral" parameter.
The server is configured as a consumer for this suffix:
==============================================
dn: cn=replica,cn=O\3DUPPERCASE,cn=mapping tree,cn=config
objectClass: top
objectClass: nsds5Replica
cn: replica
nsDS5ReplicaRoot: o=uppercase
nsDS5Flags: 0
nsDS5ReplicaType: 2
nsDS5ReplicaBindDN: cn=replication manager,cn=config
creatorsName: cn=Directory Manager
modifiersName: cn=Multimaster Replication Plugin,cn=plugins,cn=config
createTimestamp: 20230603080558Z
modifyTimestamp: 20230615120958Z
nsDS5ReplicaId: 65535
nsState:: //8AAAAAAABN/4pkAAAAAAAAAAAAAAAAAAAAAAAAAAABAAAAAAAAAA==
nsDS5ReplicaName: 68a75783-01e511ee-9ffab29b-2dbcec18
==============================================

I cannot reproduce the issue when the suffix is not replicated.

2. Run the healthcheck command:
$ dsctl <INSTANCE> healthcheck

3. Check the results.

Actual results:
Misleading messages.

Expected results:
The suffix is correctly configured so there should be no error message.

Additional info:

The same error message is repeated several times for the same backend:

$ dsctl GSS_EMEA healthcheck | egrep "DS Lint Error: DSBLE0001|Check:"
[1] DS Lint Error: DSBLE0001
Check: backends:uppercase:mappingtree
[2] DS Lint Error: DSBLE0001
Check: backends:uppercase:mappingtree
[3] DS Lint Error: DSBLE0001
Check: backends:uppercase:mappingtree
[4] DS Lint Error: DSBLE0001
Check: backends:uppercase:mappingtree
$