The majority of their mt's come from third world countries where workers are educated somewhat but English is not their first language. Because of this they don't have a grasp of idioms or slang of any sort. Nuance doesn't assign a team to a particular doctor or clinic so no one ever works on one doctor long enough to learn his/her accent, frequent sayings, local idioms or drugstore names, etc. Nuances quality control just sucks. The things that get by and become part of a patients record are just shocking. And the physicians allow it by not following up and making sure everything is correct.
Also, because most of their MT staff comes from outside the US, they can pay them dirt cheap. This hurts the US MT's because now Nuance, and all the other transcription agencies, don't want to pay a decent wage to US MT's because they can get labor MUCH MUCH cheaper by hiring in third world countries. Since the physicians aren't putting their foot down and demanding better quality in transcription, all these transcription companies hire the majority of their mt staff from outside the US.