That's the way its supposed to work. Things you'll find in the owner's manual:

- Middle position is called Normal mode. This is your default ride height.
- Lower position is called Access mode. This is for ease of ingress/egress or loading the vehicle.
- Higher position is called Off-Road mode. This is used when you need more ground clearance.

All modes, except Normal, is temporary. Above a certain speed, around 20mph, it goes back to Normal mode.

In order to manually change modes, certain conditions need to be met:
- Engine must be on.
- Doors must be closed (except tailgate/liftgate).
- Vehicle must be below speed threshold.

Wow, I pretty much regurgitated what's in the manual. Please go read your manual. That's what I should have said instead!

As far as overriding things. Quick search will net you different options. Good luck!