I'm on my phone so I can't share a save but I've tested in a few games and it doesn't appear to be specific to a single save.
Anyway, I've noticed when setting up racing in the current build it can be next to impossible to select a vehicle or engine to race with. When clicking the button the chose your car or engine nothing happens and obviously, you can't start racing without having a vehicle or engine to race with.
Sometimes this can be fixed by either trying to select a different race (switching to engine instead of car or the other way round) or by leaving the race screen and returning. Though this doesn't always work.
Anyway, I've noticed when setting up racing in the current build it can be next to impossible to select a vehicle or engine to race with. When clicking the button the chose your car or engine nothing happens and obviously, you can't start racing without having a vehicle or engine to race with.
Sometimes this can be fixed by either trying to select a different race (switching to engine instead of car or the other way round) or by leaving the race screen and returning. Though this doesn't always work.