Diagnosis
Grease and food particles have accumulated on the heating elements or the internal fan impeller. This burns off during heating.
How to Fix It
Unplug and let cool completely. Remove baskets and crisper plates. Use a damp microfiber cloth to wipe the interior walls. For the heating element and fan, use a soft-bristle brush (like a clean paintbrush) to gently dislodge debris. Do not use water or cleaner directly on the element or fan motor shaft. Wipe out loosened debris.
If That Didn't Work
The smell may be in the non-removable air path. Place a bowl with vinegar and water in the bottom basket. Run a 15-minute bake cycle at 300°F in the bottom zone only. This creates steam to loosen internal grease. Wipe out thoroughly afterward.
Heads Up
Never submerge the base or let liquid enter the vent openings on the top rear. Do not use metal utensils or abrasive pads on the heating element. It is fragile.