Yellow flame also means there is contaminants entering the gas stream.
You can clean out the line with pipe cleaners when the line is un-loosened, but the rust quickly comes back...also the pilot or burner orifice can be cleaned out with a size smaller drill orifice bit or a fine gauge wire. The older units used a steel gas line which rusted and flaked off horribly, I replace it with an aluminum one.
Most full service propane
companies will do it for you...an R.V. specialist is not needed here.
The whole set up is basically cheap online if you want to order it and just R&R it all, it often is the results of living in moist areas 5+ years or more.
Having stuck nuts and difficult to move parts is normal in this area of service.
[b]Tip: It is tempting to try to use spray chemical products that unloosen these parts...do not.
Bench it... use multiple wrenches holding the component steady and applying force at the nut at same time in the correct rotation opposite of each other. An electric solder iron when the refrigerator is on the bench placed on the stuck nut a few minuets heats up the metal enough to expand it so it breaks free...this of course means no L/P is present.
I disconnected the gas line and removed the burner today. It was full of rusty scale particles. I could not get the gas jet out without destroying it and didn't see anyway to clean out the burner without removing the jet. So I need a new jet and perhaps it may work now.
I also got to test the igniter and could easily see the spark with the burner moved out in the open.