You know, that freezer smell. It doesn’t smell like rotten food. It doesn’t smell like fish or meat or vegetables. It doesn’t smell like anything that can be readily identified, except…funky freezer.
I really don’t want to defrost the damn thing the whole way, but I guess that’s the only answer? Then swab it down with vinegar solution followed by baking soda? Have I answered my own question here?
I keep a box of baking soda in the fridge for odors. Maybe that would work for the freezer as well.
After you’ve cleaned it out of course.
Pretty much, as much of a PITA as it is.
Then once it’s clean a box of baking soda will help keep the funk down. I use the fridge/freezer boxes that have the open panels on the sides, and don’t have much trouble with freezer funk.
I used charcoal briquettes to clear rotten food stench in my freezer and fridge once. (The joys of having the power go out when you’re on vacation–YAY!!) Worked FAR better than the baking soda we tried with virtually no success for several days. I just placed a briquette on a jar lid and put one in each section.
If charcoal can clear THAT smell, maybe it would work on your freezer! 
I had this issue the other day! Should get bs the next time I shop.