This is a one-time issue that Jack explained in a separate thread. Car design will return to normal when your new season ends and the next season begins.
Jack
My apologies, but this may be how this season has to run (just this one). There was a problem with the code that reset seasons and it existed for around 24 hours. It was significant enough to stop some leagues from having a new season at all. It's fixed now, so won't happen again for all future seasons.
As I was repairing this manually and resetting seasons by hand, it clearly reset the season twice in your league, resulting in a 'double design reset', initially to your next season designs, then to the next-next season designs which wouldn't have been generated yet, resulting in 1 for all attributes. At this point the only relief I can offer is that it should be the same for everyone in these leagues and will only be for this season.