On my 2020 Miramar, when you remove the return air grille right under the refrigerator you see the heater behind and the air ducts that go into the floor right in front of it. These under floor ducts typically go toward the back and one toward the front in the floor. In mine, they had not properly installed the duct fitting on both of them and I had to remove and re-install.
And vacuum the sawdust out of it. And then vacuum it again. Still pushes out sawdust, so much for the factory cleaning anything. Lots of posts on that subject.
After I reconfigured the flex ducts to eliminate a twist and took a bit of time to secure and seal everything they work much better.
__________________
|