Oracle Reactive Streams Ingestion - SEVERE: Invalid timezone

I have a very basic java test application where I use ReactiveStreamsIngestion to inject data into an existing table

This is working fine for a database with dbtimezone UTC but as soon as I try to run it against a database running in another dbtimezone I run into:

SEVERE: Invalid timezone
oracle.rsi.RSIException: Invalid timezone

And that seems to occur already at connection level. Thus even when no table is used with a timestamp column at all.

Someone can give advise what to do here?

Test program:

import oracle.rsi.PushPublisher;

import oracle.rsi.ReactiveStreamsIngestion;
import java.sql.SQLException;