Usually if a caravan is listing its caused by the indespension rubber on that side either suffering damage due to potholing etc, or sagging through age, i cant understand why a new axle didnt cure the original problem, because surely any chassis damage would have been investigated already and any damage would be visible.
indespension units are very hard, if not impossible to fit in the workshop/service centre and so usually a new axle is recommended.
Also we thought a twin wheel Ace had a twisted chassis last spring because the wheel arch (plastic screw on arch) had been worn away by the front tyre, after all the measurements had been taken and found to be correct, it turned out swift were putting the spats on in the wrong place, we had a whole run of them where at least one side or the other had to be removed and realigneed correctly.