You need 10 best answers for a badge in that section, and 5 badges (at least for bronze, not sure how it works for the others) to get a bronze hammer that is displayed in all parts of the forum just left of your username.
The actual bug is that it won't tell you that you have 10 best answers. When you have more than one it says "You have (x>1) « best answer » in this section", regardless of how many you actually have. So you just have to keep track of them yourself for now. They are being recorded by the system, they just don't get reported properly on the page.
Hold your mouse over the name of the badge (example, Sophomore) and it will tell you the requirement to earn that badge. Note, the counter at left only says "one or more" and there may be a delay after earning.