> Same thing about the WW2 tank that's not working. A vehicle that doesn't work is still a vehicle.

That completely depends on your definition of a vehicle. According to your definition an object that once met the conditions to be a vehicle will always be a vehicle. You can apply Theseus's ship to the WW2 tank replacing it's parts and then at what point does it seize to be a vehicle?

If your definition on vehicle depends on transporting humans than a wagon seizes to be a vehicle. If your definition depends on transporting objects in a self-propelled way than humans become vehicles.