I also had significant problems with the heating performance in my 32RLS. Under warranty, the tangle and excess duct lengths were fixed, a second dedicated duct was added to the kitchen island plenum and an additional dedicated duct and outlet was added at the toe kick below the coffee bar. Problem solved!
The spec for the Suburban 35,000 BTU furnace requires the equivalent outflow air volume from at least four 4” ducts. The factory installation in my 2022 32RLS only have three 4” ducts. This strangled airflow frequently triggered the furnace limit switch which turns off the propane burner.
I now have five 4” ducted outlets and that actually works!