DIAGNOSIS This is mechanical interference in the harvest mechanism. A piece of ice is jammed in the evaporator grid or the ejector blades are hitting frozen-on ice.
FIX 1) Turn the unit off and unplug it. 2) Remove the ice basket and any loose ice. 3) Look into the ice drop chute with a flashlight. Use a plastic utensil (never metal) to gently dislodge any visible ice chunk stuck to the metal evaporator fins.
IF THAT DIDN'T WORK The noise may be from the water pump struggling with scale or debris. Perform a full cleaning cycle with vinegar. If the pump buzzes loudly during cleaning, it may be failing.
HEADS UP The sound of ice cubes falling is normal and can be loud. Abnormal sounds are a metallic scrape, a high-pitched whine from the fan, or a persistent loud buzz from the compressor area. Unplug immediately if you hear these.