DIAGNOSIS This is caused by overfilling the basket. It blocks the rapid air circulation path, creating hot spots directly above the heating element.
FIX Do not fill the basket beyond the recommended capacity. For even cooking, arrange food in a single layer with space between items. Shake or turn contents at the midpoint of the cook time.
IF THAT DIDN'T WORK You may be using a temperature that is too high for the food type. For dense or frozen items, reduce temperature by 25°F and increase time. Use 350°F-375°F as a baseline, not 400°F.
HEADS UP Placing a parchment paper liner or aluminum foil on the bottom of the basket can further restrict airflow and cause burning. If used, ensure it is perforated and does not cover the entire tray.