Using MariaDB Galera Cluster

Hello Everybody,
I have configured MariaDB Galera Cluster with 3 nodes (master, slave and slave) and one server with Maxscale service to control or/and distribute connection between servers. The Maxscale is configured to send request to the master when those connection will write (INSERT, DELETE, UPDATE) and the slaves will receive connections when they are read (SELECT). But it doesn’t work and I receive the follow error:
DB Error: Duplicate entry ‘dcoia9gtequ2nokl16uig8vc51’ for key ‘sessions_pkey’
In apache error:
Fatal error: Call to a member function getPrimaryLocale() on null in /var/www/submission_scielo_br_2_4/htdocs/classes/i18n/ on line 116
I am using OJS 2.4.8
Best regards,