What does this error mean?

As the error message states, an unexpected exception was caught in one of the messaging classes (InboundMessageHandler, OutboundConnection, In boundConnectionInitiator, OutboundConnectionInititator).

Why does this error occur?

There is not a specific cause for this error message. This message occurs when the exceptionCaught method catches a throwable error of some type. This is a catch-all error message.

How do you fix this error?

Because this is a catch-all message, there is no specific remedy. Start by analyzing any stack trace that may be associated with the message to determine a root cause. If the error is causing issues beyond the messaging, please reach out to Datastax Support for further assistance.