Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You sent a letter or a query to another node, and a frame came back, but it was not the answer to your request. Here is what rush expects. After you dial with letter or query, it waits for exactly one answer frame. That frame must be of the answer command. Its payload must start with a sixteen-bit code, followed by the body. And its destination must be the source of your own request, because an answer is addressed back to whoever asked, in response to the earlier message. If a frame comes back with a different command, or without a code, or addressed to somebody else, then it is not a reply to you. Perhaps it is stray traffic, perhaps a confused peer. Rush refuses it rather than treating it as your answer, because acting on the wrong reply is worse than having no reply. The message shows what was wrong in the slots. Check that the peer is running a compatible version, and that it answers the request you sent. Then dial again.
Text from the Rush engine's error catalogue.