Your platform is big that it doesn’t stay balanced for example: when you are turning left the platform will tilt to the right. Try and make a bigger rail.
If you observe games such as Theme Park Tycoon 2, you will see that the bottom the the roaster coasters would be hooked onto the rail itself, preventing it from coming of the track and allowing it to move in any direction the track doing in e.g. upside-down.