The only thing I can suggest is take a closer look at the leaf springs in the front.
They make look good but look closely where they mount to the front frame.
You are looking for a cracked leaf spring at that point.
The next thing is on some of the older rigs they put a spacer on the rear springs to level it out.
Look on the axle attaching point for a metal spacer plate on the drivers side. I have heard they do this and I believe someone here had the same issue and they removed the plate and all leveled out.
Oh I found the message about the other guys leaning and it was the spacer.
Georgetown 370TS Bath & a Half Leans to passenger side