You're playing a game in this case. Similar to scrolling to the right in a side-scroller. The game doesn't want to let you go back to the left - or in this case to re-answer the previous question.

However that doesn't mean that the back-button is broken. It behaves like it would behave on other websites as well - and actually doesn't register multiple guesses separately.

If you'd elaborate more clearly where this behaviour is broken - as generally it's not - I'd be happy to look into fixing it for your comfort...