There was a problem with file links after transferring the database from MySQL to MariaDB and performing the OJS version upgrade. It turned out that the SQL statement “select journal_id from journals” resulted in a different order of journal_id’s on the MariaDB instance.
I edited ojs/classes/install/Upgrade.inc.php to change the select statement as follows:
< $contextsResult = $genreDao->retrieve(‘SELECT journal_id FROM journals’);
$contextsResult = $genreDao->retrieve('SELECT journal_id FROM journals order by journal_id');
Once I had copied the database and re-applied the upgrade the problem was resolved.