Most but not all gas appliances in our trailers have a secondary regulator in their valves and the furnace
Could that regulator be out of adjustment
Also be careful when working around your control board, When I was working on quieting down the fan noise I killed it
My plan and it worked on the bench was using a PWM board controlled by a heat sensor have the fan speed follow the temperature inside the furnace
It worked well starting slow and as the temperature went up so did the fan speed and the converse when the flame was shut off and the temperature went down.
The result was the furnace
didn't come on and go off with a roar.
The experiment was a success but there was too much added to my liking
On my Suburban water heater the instructions are given on testing and adjusting the internal regulator no such luck with the furnace.