Diagnosis
That's the sound of the metal housing and internal components expanding at different rates as they heat. It's common, but excessive noise can mean something is loose.
How to Fix It
1) Make sure the oven is on a perfectly level, stable surface. 2) Check that the crumb tray and air fryer basket are seated correctly and aren't warped. Push them in firmly. 3) Open and close the door a few times. Sometimes the latch or door hinge needs to settle. Run it empty at 400°F for 10 minutes. The noise often lessens after a few cycles.
If That Didn't Work
The noise might be coming from the fan blade hitting something. Unplug the oven, let it cool, and look inside the back wall of the oven chamber. Use a flashlight to see if any food debris or a loose piece of foil is stuck near the fan. Carefully remove any obstruction with long tweezers.
Heads Up
A constant grinding or screeching sound is different from clicking. That could point to a failing fan motor bearing. If you hear that, stop using it and contact support.