FWIW subtitles for the original language will also sometimes vary from the original audio as well. I tend to re-watch shows on low volume with subtitles on so I've caught this a number of times, but it's fairly rare.

Usually I've seen the subtitles shorten the words in the audio. "You must come with me now" -> "Come now" or similar. I've been assuming it's to help the reader keep up with some quick exchanges.