About gaming process

 My question purely on game process

I bought the last 3 dlc package. I pumped over 2 of them, the last Movie Heroes, I opened  Dodge RT after Aston martin db5. Further opening of cars from a package doesn't go though I passed a large number of competitions on Dodge. It would be desirable to receive still Shelby gt 500, Pontiac... It is interesting to me, it is my problem or it is just necessary to pass bigger number of competitions than in two other packages for opening of other cars
Because in 2 other packages I had a fast opening of new cars, and here here somehow opens nothing therefore it disturbs me