Since you haven't found the source of the smell, it couldn't hurt to very liberally sprinkle baking soda over all of the carpet areas and leave it all day. If you can, close up the RV and turn on the a/c while you are gone. If you can't, you can't.
Vacuum the carpet when you get home going over it several times. If it lessens the smell, I'd do it again the next day or use the baking soda before going to bed and vacuum in the morning. As I said, it can't hurt. Good luck. Keep us posted. Hugs, Di