In addition to all the good advice above, look at the door seals. I was always a fanatic about keeping the fridge and seals clean with a Clorox whipedown and one day looked UP at the underside of the door seal. YUK!!! I thought I was keeping it clean but that little groove on the underside was black. Now I make sure I look at the underside and particularly that groove that gets exposed when you pull on the door seal a little.
I use the Clorox Kitchen Cleanup with bleach and my wife hates the smell and doesn't want me to use it. I told her she doesn't have a choice and the smell does go away in a few hours so just stay out of the trailer when I clean.