I've not been using the Chinese course for very long, but, while I am finding it very useful, I've noticed a lot of mistakes with the audio recordings. Now it's possible that I, someone who does not speak Chinese natively, am simply mistaken, but I thought I should mention this anyway. When I am learning a single character, the audio does not match up with the transliteration I am given; for example, what is written as "xìng" I hear as "xīng". Another example: written "shí", spoken "zhī". This only happens with single characters; when it's spoken in a sentence it sounds fine. I can work with it for now but it comes across as kind of sloppy.
You are not wrong about the pronunciation not matching up with the pinyin in many individual cases. There are quite a few. I've reported a number of them and try to keep doing it as I go along.
A problem with the reporting system is that it forces you to pick an option, when sometimes, the problem is something else. I still don't know how to get around that, but generally I comment in the nearest discussion and hope that a developer will come around some day and see it.
The following is just my guess as to why it happens; it could be completely wrong:
Maybe one and the same Chinese character is actually pronounced differently in different contexts, and it could be some sort of system limitation that the character can only be assigned a single pronunciation.