Could it be something in a wall or under the house in the area of the fridge? (Test by moving fridge to a different (undoubtedly inconvenient) location for a day or two and see if smell follows)

It's a good suggestion. However, I'm quite sure it's the fridge. We pulled it out from the wall and the smell is very strong coming out of the back vent area when the fan is running. :) Appreciate the recommendation though.

Did you ever find the smell? I believe the exact same thing is happening to ours and I can’t for the life of me figure out what it is

Same here smells like a wet old rat with one tooth living nearby. Does anyone have the answer?

Same here toxic smell worried about breathing this dam frustrating whirlpool needs to help or maybe we could sue their

Clean the condensate collection tray at bottom of the refrigerator. All brands and models of self-defrosting refrigerators and vertical freezers have them, the melted ice-water must drain away to somewhere. The collected water is evaporated via heat from the compressor. Designs vary. Some are accessible by removing the front toekick grill, others via a removable panel on back. Some trays can be pulled out for cleaning, others are fix-mounted and must be cleaned in-place.

I have the same problem and the fridge is only 3 months old. It was fine the first 2 months and started a bad smell and taste in the food - even in ice cream

It is most likely the nonstick coating of the ice tray breaking down and emitting an awful oder. It’s kind of like a tequila / mildew smell. Sweet and nasty. Makes everything in the fridge taste bad. Even makes soda cans taste bad when drinking from the can. Just replace the ice maker assembly.

Update nearly 10 years later: I still have the fridge, and it's running well. Interestingly, the smell eventually went away on its own.