This error comes frequently when lots of write operation happen on ldap server and at the same time we do the ldapsearch from our application. ldapsearch command say user does not exit in DB but user exit in DB, But after some time it's work well.
The real solution is to upgrade to back-mdb when OpenLDAP 2.4.34 releases, or grab it from current RE24 git.
--Quanah -- Quanah Gibson-Mount Sr. Member of Technical Staff Zimbra, Inc A Division of VMware, Inc. -------------------- Zimbra :: the leader in open source messaging and collaboration