I tried to export a save file for the CSR 66. Appearantly, it was impossible to load. I tried to load it myself, it failed. I tried saving lots of other cars, and they failed in the same manner.
Here’s the save file if there is possible to see what’s wrong with it…
Probably that means you’re using the wrong version of the game to make the car? Check whether you are on the default branch or openbeta branch, and what the requirements of the challenge are.
That solved the problem, I think, now I can at least load my own cars.
Sadly, it also meant that my previous work disappeared, including the car for the competition, but there will be more of them.