In 5.1.7, this index is unique (create unique index IX_3463D95B on JournalArticle (uuid_, groupId)) but in the client's database, it's showing as a non-unique index. So that explains why the duplicate entries are allowed in the database. This script will remove all old versions of JournalArticles and only retain the newest therefore satisfying t…

upgrade_lr5.1_lr6.1_fix_journalarticle_index.sql

drop index IX_3463D95B on JournalArticle;

create temporary table temp_ja
	select * from (
		select groupId, articleId, uuid_, type_, max(version) as 'maxVersionId', count(id_) as 'countId' from JournalArticle ja
			group by groupId, uuid_
		) temp
	where temp.countId > 1;

delete ja from JournalArticle ja
	join temp_ja as tja on tja.groupId = ja.groupId and  tja.uuid_ =  ja.uuid_ and tja.articleId = ja.articleId
	where ja.version < tja.maxVersionId;

drop table temp_ja;

create unique index IX_3463D95B on JournalArticle (uuid_, groupId);