Resolution:
Symptom:

BE SendEvent activity fails when the destination Queue and the TopicConnectionFactoty is not defined in the JMS connection advanced tab.

Following is the stack trace in designer console:

===========================
java.lang.ClassCastException:
      at com.tibco.cep.driver.jms.JMSChannelConfig.getTopicConnectionFactory(JMSChannelConfig.java:475)
      at com.tibco.cep.driver.jms.JMSChannel.connect(JMSChannel.java:174)
===========================

Reason:

BE's current behavior is to have a valid set of Factories specified in case of using JNDI. It constructs the connection upfront, to optimize the runtime.

Workaround:

Create the TopicConnectionFactory and set it in the Advanced tab under the Shared JMS Connection