The failure mode is ordinary. The phone rings during Friday afternoons and the day before a holiday, when cassettes run out together, nobody answers, and the lobby machine stays dark through the Friday rush.
Grit answers and writes the terminal id, the error, and how many cassettes are empty before talking about a clock time. The Cassette note count turns those counts into notes to stage so the company sees a size, not a vague "can you come look."
Then one company is offered the note. A local tech swaps the cassette or the comms gear. Grit does not carry cash. If the window cannot be met, the caller hears the next real opening, not a promise that keeps the board pretty.
The note is the product. A callback that skips the terminal id, the error, and how many cassettes are empty creates the second angry call.
