Rollercoaster Building

In science class there were 2 experiments that were tested on was to find the maximum velocity of the ball and the other was to make a rollercoaster yourself. In the construction and testing of the rollercoaster that was built there was a problem that the ball would not go down the next hill so it was cut so it would work and go all the way down. A problem with the testing was that when the clamps were put on the track, the track would become too small for the ball and the ball would fall off. This problem was changed so that when the rollercoaster was tested the clamps were held in place instead of attached. The total energy of the coaster seems to be decreasing. It is decreasing because at the highest potential energy to the highest kinetic energy some of the potential energy is being converted to thermal energy before it reaches the highest kinetic energy. So it seems to be decreasing, but it can’t because of the law of the conservation of energy which states that energy can not be made or destroyed.