Robert,
First, what were the conditions you were driving under. High winds, bad weather, towing, etc.
If towing, and the toad is not properly set up it can add significant sway to a unit. There are many posts on the forum when folks tried traveling with winds in excess of 15mph and they had a rough time. I would check with the chassis manufacturer and they should be able to tell you if there is any change from 2019 to a 2021 chassis which would preclude you using the model parts designed for the 2019. The body builder, be it Fleetwood or any other brand is less likely to know any small changes in the chassis that would come into play.
While all the items you listed are often used on older coaches, many are incorporated into the newer coaches, so knowing the totality of what you were facing would help folks to give you a better answer.
