This seems to be a regression as 6.1 GA does not show this behavior.Under load (many producers and many topic subscription) the broker will start to raise the following error in its log| javax.jms.JMSException: Unmatched acknowledge: MessageAck {commandId = 0, responseRequired = false, ackType = 2, consumerId = ID:mac.fritz.box-50412-1412792479100-1:2620:-1:4, firstMessageId = null, lastMessageId = ID:mac.fritz.box-50412-1412792479100-1:2557:-1:1:136, destination = topic://stress.publisher-661, transactionId = null, messageCount = 1, poisonCause = null}; Expected message count (1) differs from count in dispatched-list (255)|

This seems to result in a loss of messages.