To be honest, I can't remember there being too many instances where the Broncos could have challenged something only to ignore it or have used it up on something trivial. The only incident that comes to mind is the Corey Oates being dragged over the sideline against the Gold Coast and even then replays showed the touchie actually got it right.
The Broncos actually came up with one of the best challenges of the season to deny the Warriors a try. They also had two other incidents that should have been successful against the Raiders and the Panthers but the video referee completely botched it. Annesley admitted to one, but from memory never said anything about Nathan Cleary knocking the ball on.