Need fOr speed the rivals on ps4

When playing this game and I want to unlock the bonus cars 1 in racer and 3 as police I do the challenges it asked and they all unlock great :-). So I save progress and turn of ps4 to my horror all 4 cars become locked again. I think I have not saved it and my ps4 is at fault. So I check my game details and it states all my cars have been unlocked and I was on level 17 on over watch and I have completed the game 100%. Why did It re lock my cars is this a common problem can it be sorted as it won't let me do any more over watch challenges please sort this