There is no way to sugarcoat this. The game construction is very poor and unacceptable. At the four points where the track connects, the car is very hard to move past. As a result the car can jump the tracks. As others have said if you move the car slowly it does better at counting. But if a 4 to 5 year old is trying to get it past one of the four connection points, he has to give it a good push. This usually results in the car counting wrong or worse the car coming off the track.
The counting issue also happens if you don't push the car very smoothly. This is not easy for a 4 to 5-year old. Especially for long moves, he pushes it part of the way, then re-adjusts to push it the next few spaces. His arms just aren't long enough. As others have said this may happen from the car registering multiple times on the same bump. Also moving too fast may cause the car to lift and not register on a bump. Mom or dad will need to hold the track to prevent it from moving when children are moving the car.
Hasbro should have spent a little more money in making the track. The car, houses, and money are fine. The concept of the game is fine for a 4 to 5 year old. The money really doesn't matter for winning, but my son does like it when mom or dad have to pay him though.