The MQ Gateway sometimes forwards a tcp conversation from one messaging client to two different broker instances. The broker instances are part of the same Fabric broker group though.
In return the Gateway also forwards the responses from both brokers back to the same single client, violating the spec of the messaging protocol used (AMQP in this example).

I have evidence of this in the form of tcp dumps that capture the conversation between client - gateway and gateway - broker. Will attach these in private comments.