I've noticed that sssd has incorrect behavior with different versions of LDAP.
The issue is because of LDB store each entry in case sensitive format,
but there's no difference for LDAP, so if we have in LDB database:
and user's group entry:
then user "user" will never be a part of group "group" as entries
"uid=user,ou=GROUP,dc=domain" and "uid=user,OU=GROUP,dc=domain" are
not equal(in LDB logic).
I've noticed this when had migrated from FDS v.1.2.3 to FDS v.188.8.131.52
as last one converting DN attibutes to lower case, but provide value
of "uniquemember" as is.
You will find a patch to fix this on sssd side in attach.