DIAGNOSIS The ice is likely fused together in the basket. The ejector arm is straining against a solid block.
FIX Unplug the machine. Empty the entire ice basket. Manually break up any large chunks stuck together. Restart. The noise should return to the normal thud of cubes falling.
IF THAT DIDN'T WORK The noise could be the ejector blades hitting the evaporator plate. This happens if the unit was moved while making ice, misaligning the mechanism. Unplug, remove the ice basket, and gently press the evaporator plate to ensure it's seated flat.
HEADS UP This model is inherently louder during the harvest cycle than some others. A loud motor hum and a distinct “thunk” every 10-15 minutes is normal operation.