One fictional message. Bytes are counted on this card, not captured from a network.

Positions 1 through 28: the request the backend accepts as complete.
Positions 1 through 40: the request the frontend accepts as complete.
Positions 29 through 40: inside the frontend's request and after the backend's request.

The card does not write a second request into those bytes.
The failure is that the two peers disagree on the end.