System Synchronization Issue with Error 40010000 and FTJR2008. [XBOX]

So yeah I just wanted to launch the game and then theses error appeared. I don't know why or how, unable to play online, so then I searched deeply and found that it might be a car that is corrupted and you should remove it.. Guess what? The car I found duplicated in my inventory was the Porsche BP police edition... No way to remove it, took me a day to remove it (I think since I don't see it anymore) by selecting the vol 8 pack (containing the car), uninstalling it, reinstalling the pack while the game is still open, press the Xbox bouton when it says "ready to use/play" and then loading at the bottom right, checked the police garage and it was vanished, I was happy and thought I was a genius! Until I tried, nothing, maybe going back to the select mode lobby in the game? Nothing. Maybe re launching the game? Nothing. Same error everytime. And now I'm stuck with that and I don't know what to do. Any tips?? 

( I heard there are not only duplicates cars that are the problems but also bugged cars and idk if the bugs or the corruption is visible on the car, if yes what is it? Thank you.)