The reason is not that the pads have been fitted incorrectly. Sometimes problems called fading arise. Fading causes a loss of effectiveness when the brakes are hot. This is a problem with the friction material, the quality of which is not very good. To avoid this problem, do not overuse the brakes. It is better to use low gears when going down steep descents, using engine braking rather than brakes. Unnecessary use of pads can cause overheating and damage to the brake discs. Another way is to put the pads on after scorching (heat treatment), which will eliminate the fading effect.