Ok first folks the 12 volt everchill is a compressor refrigerator. like a residential. the Hot coils are on the back near the bottom..
My guess is the original was also a 12 volt compressor and the body builder did NOT provide proper ventilation for the hot side... (No vents on the outside of the Trailer behind the thing and it's installed "Tight" inside with no vents there either) there are ways to fix that but they require modification of the mount and/or the side of the trailer.. Without more (Eyes on) Information I can't say for sure.