I got this Domino console error “Error locating a Domino Directory entry for certifier /O=DomainName: Entry not found in index” from time to time.All group authorizations are not working when this happens.
After a million fixups and “edits&saves” of the certifier in names.nsf it worked again. Not anymore.
Not sure if this will help your issue but I had the same error on my sametime server but it seem to cause an issue, but it would not stop sending the errors. I ran load updall -R names.nsf and that didn’t seem to help so in a fingers crossed mode I did a fulltext index on the names.nsf and waited until the next day and ran load updall -R names.nsf again and tada, all my errors went away. But it still returns after the server runs for a day or so, I think it tells me it is something with the server and how it is reading the docs.