Hi Polanski,
Welcome to the Heartland Owners Forum and maybe to the family. We have a great bunch of people here with lots of information and all willing to share their knowledge if needed.
Your "service advisor", who ever that may be, needs to play catchup about the units his dealer is selling. There were a few, 3--4 years back that had a problem with sagging tanks and a couple did get down on the axles I understand, and it was only on one line of 5th wheels, but that has since been corrected and no more problems. I do not know of any problems like that on the Northtrails.
Enjoy the forum.
Jim M