Gearbox gear repair. It seems to be a fundamental problem for the product. All the problematic products are the same gear problem. The two gears in question must be repaired by opening the gearbox. It would be easy to get the same gear, but... A gear is cracked. The thickness of the steel pipe in the middle is larger than the gear hole, resulting in a crack. Secure the cracked gear with glue and expand the hole. Grind steel pipes to make the hunger thin. https://youtu.be/4QJFvA5n3gs 업데이트 (2019년 10월 23일): The cracked side of the gear needs to be cut and glued. This ensures a constant gap between the teeth. 업데이트 (2019년 10월 23일): The gears were first disconnected and then polished the bumpy part of the metal pin.Cut off the cracked part a little and fix it with a force adhesive. Apply a little glue to the metal pins and fasten them with the gears.