We using a three node mariadb cluster for currently more than 130 Webservers.
Between the db-nodes and the webservers is a proxysql server as a load-balancer, which
is mainly used for high-availibility purposes for the db-cluster. Thereby only one db node
is used for all traffic from the webserver to their corresponding databases in the cluster
(a read/write split is not yet implemented/used).

On a set of the webservers we are using an CMS which uses Apache/Tomcat/Java. The
current version of this CMS is using the mysql8.0 jdbc driver and this can't be simply changed
before initial installation.
We can see that the writing statements didn't get replicated on the other two nodes.

If we switching to the mariadb jdbc driver after the initial installation all data is replicated
and everything is working fine.
By switching back to the mysql jdbc driver we can reliable provoke the behaviour (no replication) again.

Finally we are currently don't really know wether this is really a mysql jdbc driver specific behavior or wether we are facing some serious problems with our replication.