I've no idea how a fridge works, but do know that odors in it circulate AND that usually there is a culprit/source but it can be difficult to detect after the stink gets into so many other things from egg crates to ice cubes to unsealed items, basically anything porous even paper labeling on glass made - So when it happens I clean out the whole thing, wash the outsides of all containers, make new ice cubes, toss any questionable foods and then place several boxes of baking soda towards the back of the fridge -
Nothing permanently gets rid of what to me smells like water that's been sitting and collecting odors from the fridge, it has sort of a chemical and food mixed together "scent", sort of like the chlorine from the water from the tap mixed with produce market smells - After cleaning the fridge out it goes away but eventually comes back -