I have two processes.
One process has a loop. In a loop it creates a temporary queue A, and sends a message to a permenent queue. The message contains replyTo field as this temporary queue. Then it receives a message from the temporary queue.

Another (second) process listens to permanent queue A, and receives messages from there via an attached message listener (asynchronously). Once the message it received, another message is sent back to the temporary queue which is in the replyTo field of the first message.

When I do that in a loop, what happens seldomly is that the second process does not get the message from the first process. So, the first process waits.

If at this point I start another (third) process, logically equivalent to the second one (also listening to queue A visa onMessage callback in message listener), it gets the message.

Do you know what could be wrong?

It is not too easy to reproduce this example with simple code, though.