I pushed one corner down too hard and cracked my passenger window once, and learned an expensive lesson. But in the middle of a repower I was surprised at the damage done over the years from the jacks torquing the bus at various times. The frame had a wrinkle on the drivers side, and the front access doors did not close well from the body being tweaked. Bluebird understood the problem because I think on newer birds they eventually moved them from the very front as on my 1981 back to the wheels. [
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You can cause twisting in the newer models, as well. Always try to operate the jacks in pairs. One side or one end, never diagonal.
I see reference to other RV's having only three jacks with one in the front to avoid the problem.
You can still twist with 3 jacks, you’re just not as stable when they’re set!
While you’re lessening the twisting motion when the uneducated use a 3 point jack system, you definitely still get twisting of the frame. While it may be minimized enough to eliminate cracked glass, you’re still getting it. Proper utilization of a 4 point stabilization system will always eliminate issues AND be much more stable.