Why is "a" required for the second noun? This seems like an English issue and not a Czech one. (I would say "are you a boy or girl", never "are you a boy or a girl", the former was marked wrong).
This is strange. I did change this sentence a week ago. I a not sure if I changed exactly this, but it has been supposed to be accepted at least for a week.
Still we have a report just a few days old. I will try to persuade the system to do what it should do.
In English, you say a boy or a girl. If you ommit the "a", the issue might be on your side rather than on the side of the language