Due to long-distance transportation or transfer, it may cause abnormal noise and dislocation of the internal gearbox. Because it is an all-metal gear, under normal circumstances, it is louder than plastic gears.
Solution:
1. Disassembly
2. Rearrange the metal gears in the gearbox
3. Normally, the torque of metal gear is greater than that of plastic gear, but the relative sound is also a little louder