both 'chicken thigh' and 'thigh of a chicken' mean the same thing. and both versions appear throughout the course for 'paja la kuku', however sometimes one is marked as correct or incorrect. Reported (numerous times, including 13 Aug 2017)
I am pretty sure they don't have an army of developers working overtime to get all the errors fixed to a deadline. It's a few volunteers working on it when they can. So I trust that they will get there eventually. There is certainly a lot to fix.