Sometimes fast and slow audio have significantly different pronunciations
Well, I've noticed it with the word "grand" specifically.
In the phrase "L'homme grand est suisse.", in the fast-spoken French, "grand" is clear, but in the slow, the word "grand" has two syllables, and actually sounds like "bo-ron" or "mo-ron". It sounds nothing like "grand". I've come across this twice as I've gone through the lessons.
Here's a link to the slowed-down audio:
(Take off the speed variable above to hear it at full speed.)
There are correct examples of this due to liaison. In the slowed down version the words are spoken alone as if there is no context. So, in the example cited there should be a difference because of the liaison with est. Sometimes there are just poor sound files and one or other example is very hard to interpret. I haven't been reporting them but we probably should.
I have noticed this too. I thought it might be due to liaison. I don't understand liaison very well, but it has been mentioned in some Questions and Insights as a system under which otherwise silent sounds appear when words are spoken consecutively, changing their pronunciation.