Double check your math on the other fields and you will probably find those checks to be "wrong," too.
No I did not find anything else to be "wrong". Everything else is OK, just the last one digit (Composite check digit) in the challenge key is wrong. I checked it many times.
In the reference PDF-s there are two examples of keys (red digits are first four check digits and yellow is the Composite check digit):
These two examples are correct and comply with the description how to compute check digits, but if I do exactly same with the key from the challenge I get 2 in the place of the last digit.
Maybe the document is not poorly written, but perhaps just written for people that are highly involved in that area of "readable documents" and do not need detailed description.
EDIT: There was a DarkFibre's post before this one. This is the response to his post, that has disappeared.