Every hour or two, big BUZZ noise comes from back side of refrigerator. It sounds like a 2 second clicking noise. I opened the panel and it seems this buzz noise is not from PCB board WKKT Model:0158-05-05 (I am not sure this is mother board) located on the right low corner of the panel if you face the back of referigerator. Instead this noise seems coming from the middle center of the refrigerator.

If I reconnected power to the refrigerator, the noise started immedeatly and lasted about 2s.

The refrigerator works OK. But the buzz noise is annoying.