NoFrost refrigerator smells bad - where is the smell coming from?

I had the same issue - the smell usually comes from the drainage system that removes moisture in NoFrost models. The small drainage opening or the tube below it can get clogged with mold or food debris and start stinking. Check the back bottom of your fridge to see if there's an opening - you can clean it out with a cloth or a thin brush. If that doesn't help, it could also be the evaporator pan (where the water collects); just take it out, rinse it, and disinfect it.

The drainage system is really often the culprit, but try checking the back wall of your fridge - with NoFrost units, condensation tends to collect there, stagnates, and starts to smell. Pull the fridge out a bit, see if there's water or dirt buildup back there, and wipe it down thoroughly. Usually that's all it takes, and the smell is gone.