An RV dealer is not going to care about chassis problems, what you got from them is the typical answer when they don't want to be bothered. Take it to a mechanic who specializes in suspension work, or to a big rig mechanic and get their opinion.
My 87 Southwind had noise, but replacement of the old wore out rubber bushing in various places stopped the noise.
An 11 month old rig should not be making noise in the suspension. There is something definitely wrong and it needs to be looked at by someone who is competent and if your dealer had been doing their job competently, they would have told you what I have just told you.
It may cost you some money to get it looked at, but you can then go to the manufacturer with a warranty claim and make them fix the problem when you know what the problem is.
In fact you may want to contact them first, they may even pay to have it looked over to save your that cost. At 11 months you do not have much time to waste in getting it fixed because once you hit that 1 year mark, no one is going to touch it, the cost to repair is going to be all on you.
Good Luck, and be persistent, so if this drags on beyond the 1 year mark you already have a case going and can keep pushing the issue.
Berniece & Russell with LilBit a Netherland Dwarf rabbit
1987 Southwind, 1995 Ford F150 Supercab 4X4 toad
Life in the fast lane? No thanks! We will stop and smell the flowers at every chance.