It was impossible to replicate the bug today so I've set 1.24 live. Because whatever bug was there was also in 1.23 so you might as well play the latest version while we track the bug down.
So, here's what I think happened: carn1x reported a bug crashing the game after races sometimes a while ago. What these situations have in common is that the player passes by a leaderboard call to steam. So when steam doesn't respond with good data, the game can crash. So we'll put our efforts there instead, simulating what happens in the game when steam doesn't respond with what we expect and I'll think we'll find our culprit in both scenarios at once!
Thanks for your patience, we'll try to resolve it asap. In the meantime you should be able to play but may encounter occasional crashes after passing by leaderboards screens/record uploads. Going offline in steam should make it completely safe but that's not a good solution obviously..
Hopefully 1.25 comes soon with a fix.