Isn't it your responsibility to provide the correct foundation for your spa?
With ours, it was clearly spelled out in several places- the warranty, the owners manual, etc.
Did you have a pre delivery site inspection, and if so, did they check your base?
Just curious. Sounds like your patio isn't up to snuff for spa support. I think that it's pretty important your base support the spa evenly. It may not have to be absolutely level, but it should fully support the spa.
If you are as out of level as you say, I'd be scared that the spa isn't being supported fully. Bet your warranty will not cover damage from an insufficient foundation.