You probably hit defect 16737497 that impact indexing.
I would recommand to install the latest bundle patch for ODSEE (22.214.171.124.1) (Oracle Fusion Middleware Bundle Patch Release Notes for Oracle Directory Server Enterprise Edition - 11g Release 1 (11.1…)
The bundle patch is available from My OracleSupport portal.
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Thanks! I will plan for the patch... but it is interesting that some of the searches were not returning any search result though they exist in the database because i took export and saw the entries. So i thought i can try re-index the database but that did not even help. So i had to reload the entire database. Once i reloaded the database the same search return the expected results.