I'm surprised to hear this organisation is successfully doing ML speech to text. Is it running 100% of volume in production? Or is it more of a pilot type thing? I know of a French multinational bank that just tried for 2 years to get a ML speech transcription up and running, for transcribing conversations with customers, but due to unreliable results, recently put the project on ice. Their experience was much along the lines of everything discussed in this comment thread.