When running the TCK test com.sun.ts.tests.jms.ee.ejb.sessionTtests.Client, the clientID is not originally set, but it is present in JBM_USER table in the record for the user the connection is using. Thus, it gets set, but it fails later in the code, with the exception "Cannot set clientID, already set as %s". But, as you may expect, we are talking about the same clientID, because it is the same source. So, it may be either a problem in TCK (which should use a connection factory which have an empty clientID), or a problem in the messaging implementation (which should ignore this "setClientID" if it is not changing). If the later, then a correction may be something like the below code (class org.jboss.jms.server.endpoint.ServerConnectionEndpoint):

From:
if (this.clientID != null && failedNodeID == null)

To:
if (this.clientID != null && failedNodeID == null && !this.clientID.equals(clientID) )