Jack
If you click edit above the pit crew on training, they were all set to 'Skill' training only. Their skills are already maxed out which is why it always said no change / no gain. If you set them to 'All' or any other group they train fine. I've confirmed this on your account and sent you 50 Tokens so you can heal them.
I'll come up with a way to make this clearer in the interface in future.
Thanks Jack