When has your backhand 'broken down'?
If you hit a weak forehand that sits up in the middle of the service box and your opponent blasts an inside out forehand so hard to your backhand that you can barely reach it with the tip of the frame when all-out sprinting and stretching for it, thus you make a backhand error, has your backhand broken down?
If your opponent smashes at your body (vaguely at your backhand), and you fail to get out of the way in time to hit a backhand, thus making a backhand error, has your backhand broken down?
If your opponent hits a really sharply angled volley to your backhand, forcing you to come up with a passing shot winner on the dead run, and you fail to pass (you hit it so that he can volley away for a winner) - has your backhand broken down?
Basically, does any sort of error from the backhand, regardless of situation, mean that your backhand has 'broken down'?