What is your base made from? Sand? If so, its possible your sand is not the same depth all the way around - ours is deeper on the E end of our pool because we put more of an extended cove out into the pool on the W end with the sand - but the walls/uprights/rail are all level. Some people dish out their pools on one side or another or in the center.

I believe that the important thing is that your walls/rails are level all the way so that there is equal support all the way around and something does not buckle.