Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
Every being in rush ends its story with a signal, a small code that says how things turned out. This message is about that signal being written twice, or written wrongly. Here is the rule. The signal is written once, at the moment the outcome is known, and from then on it never changes, just like a dimension. It comes from the vocabulary in signal.feml: either a listed code, or a refusal id used as a signal. There is exactly one door that writes it, the fedex's signal door. And that door says no in two cases. First, if the being already has a signal, because a second outcome would make the first a lie. Second, if the code is not in the vocabulary, because an unknown code means nothing to anyone. Think of a verdict handed down by a court: once it is on record, you do not write a different verdict beside it. The message names the being and which case it was. If you are building the engine, remove the second write, or use a code that is declared.
Text from the Rush engine's error catalogue.