Smart Connector destination Transformation Hub

Installed Arcsight 2020.3 platform on 3 servers with one master/worker and two worker nodes.

Products are up and running, but we are haveing trouble setting up a TH destination on Smart Connector.

We follow the documentation which is trivial, but get "SSL handhake failed" when setting up a destination and on TH Kafka we get

[2021-01-14 15:04:49,641] DEBUG Got ping response for sessionid: 0x1000ce251f30019 after 0ms (org.apache.zookeeper.ClientCnxn)
[2021-01-14 15:04:51,569] DEBUG [SslTransportLayer channelId=172.16.53.92:9093-10.x.x.x:55455-261 key=sun.nio.ch.SelectionKeyImpl@6509c347] SSLEngine.closeInBound() raised an exception. (org.apache.kafka.common.network.SslTransportLayer)
javax.net.ssl.SSLException: Inbound closed before receiving peer's close_notify: possible truncation attack?
at sun.security.ssl.Alerts.getSSLException(Alerts.java:208)
at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1647)
at sun.security.ssl.SSLEngineImpl.fatal(SSLEngineImpl.java:1615)
at sun.security.ssl.SSLEngineImpl.closeInbound(SSLEngineImpl.java:1542)
at org.apache.kafka.common.network.SslTransportLayer.handshakeFailure(SslTransportLayer.java:866)
at org.apache.kafka.common.network.SslTransportLayer.maybeProcessHandshakeFailure(SslTransportLayer.java:904)
at org.apache.kafka.common.network.SslTransportLayer.handshake(SslTransportLayer.java:290)
at org.apache.kafka.common.network.KafkaChannel.prepare(KafkaChannel.java:174)
at org.apache.kafka.common.network.Selector.pollSelectionKeys(Selector.java:547)
at org.apache.kafka.common.network.Selector.poll(Selector.java:485)
at kafka.network.Processor.poll(SocketServer.scala:893)
at kafka.network.Processor.run(SocketServer.scala:792)
at java.lang.Thread.run(Thread.java:748)

Any hints ?