I had an annoying rattle coming from under my Fourwinds 24F. It came and went but was more pronounced on bumpy roads. Come to fine out it was a bolt holding the rear tire mud flap hitting my propane tank. Bolt was 1-1/2 inches long when it needed to be only 1/2 inch. Replace it and all is well. So if you have a rattle that sounds link a metal pan in the stove rattling it might be this. Hit the mud flap and you will know right away.
That could have spelled disaster after a while. Good find!! Get one of those thick, stick-on felt pads for chair legs and stick that on the LP tank in that spot just in case there's still a little silent rubbing going on with the flexing of the mud flap.
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie