The Coding Contract description for HammingCode mentions wikipedia article as refernece.
However, in-game uses slighty different coding scheme than wikipedia article.
Namely, we add one extra parity bit at the very beginning of binary string, compared to wikipedia article.

It seems that in-game scheme is also used widely as it has its own advantage (i.e. SECDED).
However, for players, they have hard time when their implementaion which follows wikipedia article doesn't work well.

I think clarifying difference on scheme between in-game and wikipedia article will be helpful.