TO Yuttapol
Very good.
The most common failure to the gear also could come from the misalignment of motor to the gear. Due to it is very long shaft, ,by be 4-5 meters. That I have seen the coupling failure, or the gear box failure at many time. During the repair, we found the installation is miss alignment. If that contactor did not have a good alignment tool, for the long shaft. Then we might face that situation.
Furthermore, do we able to do the Laser Alignment