DIAGNOSIS: This is almost always the metal air fryer basket or tray vibrating against the inner walls of the cooking pot at high fan speeds. Loose fit or lightweight food (like fries) allows it to chatter.
FIX: Ensure the basket or tray is clicked securely into the handle assembly. Don't overload it—spread food in a single layer. For lightweight items, place the solid perforated tray (not the basket) on the bottom to weigh things down.
IF THAT DIDN'T WORK: Remove the air fryer lid and check the fan blades for any obvious food debris (like a piece of onion skin) that could be hitting the housing. Unplug the unit first.
HEADS UP: A high-pitched fan noise is normal. A loud metallic rattling is not. The noise won't hurt the unit, but it's inefficient and annoying—fix it to prevent uneven cooking.