Ok, thank Jeeves for clarifying this.
So, when we cannot tab the bonus while having at least 2%, it's a bug

* I don't know, I didn't have this experience so far, but another case is when you tab the bonus, doesn't work but you have a message, something like
The crowd is cheering and your players didn't hear the orders (the + bonus).
Ok, I 'm not sure what exactly are the words
But you can read this message if bonus doesn't working, right ?
And this will happen 1-2 times in a game, not whole the game, right ?