I think you have reproduced your trigger for us.
You are simulating your own unsanitized data.
“prompt” is not talking to Whisper AI itself, giving it instructions about what it is supposed to do.
The prompt, instead, if given, should be lead-up transcription just before the audio provided, or can be used to simulate that prior audio, such as introducing a speaker or their language.
By enclosing the audio in such an uncharacteristic prefix, a suffix seems also a logical thing for an AI to conclude with.