On GitHub project, I was normally linking pull request to an issue, but suddenly after 11th pull request on create card issue, the issue appeared to be unlinkable. I tried to link to issue by "keyword" like fixes #27 but the pull request only linked to card view and bank-transactions and create card is still not linked. Also notice that their opacity differs.

What is a reason? Is it my fault?

Update

Some may say that you cannot link more than 10 pull requests but, before I successfully linked 11 prs, and other guys linked even 14 pull requests.