The last update didn't help. I finished the Pagani Royale Event, but still didn't get the car. But I started not with 0%. In the past i finished the first three stages, so I could finish it this time, but I am still waiting for the Pagani.
RR3 posted an update in FB about 8 hours ago. Grants will be rolled out based on your past progression, to compensate for this Flashback issue. If you’ve completed the event/s & don’t own the cars, you will receive the cars, with gold & VP points. If already owned, you will receive alternate rewards. This will apparently happen in phases. Both flashback events will be re run in the near future. All affected players will get xtra gold as well.
