We achieved the understanding that things may not be like how it seems. When we were asked to estimate the angle of the slope, we were guessing that it was higher than 40º, but when we had more tries, we realized that our guesses were all wrong, and the ideal and fastest angle was lesser than 40º.
The slope for the ball bearing cannot be too much, as the ball bearing would just fall and bounce off the track, but also not too low, or the ball bearing does not have enough potential energy to be converted to kinetic energy.
The accuracy of the release of the ball bearing from the start may not always be of hundred percent accuracy same for each round, as there is always a small chance of human error, like accidentally giving the ball bearing a push while releasing it, and not in the other retries and angles.
Instead of using human hands, prepare a set-up like placing a ruler infront of the ball bearing before releasing, or a machine to release the balls to ensure a fair chance for everyone who is doing that challenge.