A Casa 212-200 aircraft, registered PK-NCN, operated by PT. Merpati Nusantara Airlines as a flight number MZ 7976, departed from Ambon, Langgur for Dobo (DOB). The aircraft was airworthy prior departure. In flight from Langgur to Dobo, the Co-pilot acted as flying pilot. During the final approach at Dobo, while aircraft speed approximately 90 knots, the aircraft experienced a sudden loss of height, the co-pilot tried to correct the situation by pushing the control column and simultaneously reducing power lever. At about 100 feet of altitude, the PIC called out ?EH ? EH ? EH, I HAVE CONTROL?. The PIC decided to go around and open power. During the go around the aircraft touched the ground on the grass covered area, about 38 meters before the beginning of runway 05 and rolled about 8 meters. The area was covered by grass up to 60 centimeters tall. During this ground roll, the left main landing gear impacted to the mound about 25 centimeters high. The aircraft successfully go around and landed using runway 23, touched down about 130 meters from beginning of runway, on centre line and veered to the left of centerline. The PIC managed to correct and the aircraft returned to centerline. The aircraft stopped on the runway at 665 meters from beginning of runway 23, about 25 meters from taxi way. All passengers and crew disembarked normally on the runway. No one was injured in this accident. CAUSE: “On final approach the aircraft had a sudden bump and sank as the result of power has been reduced to counter the situation. The impact of the left main landing gear to the mound has result the left main landing gear shifted backward and out of centre.”