The ride height control arms on the rear axle control the left-right balance. Adjusted properly, there should be no lean unless you have an air bag (front or rear) that is not inflating properly (leaking, bad air inlet valve, etc.)
The use of 3 ride height valves rather than 4 is pretty much standard air suspension design, so that's not the cause of your problem. You just need to get the suspension dialed in correctly, with no leaks and properly set ride height.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC