LED lights dimmed - Whirlpool 4-Door Refrigerator

Hello There - We got this Whirlpool 4-Door French Door Refrigerator (Model #: WRX735SDBM) 1.5 year ago, and the upper LED module (with 8 LED) in Refrigerator started dimmed and sometimes they kept flickering and after few flickering the LED turned to bright as normal. However, they turned to dimmed again next time when open the door. Finally the LED module keeps dimmed with 1 LED off. We tried to replace the LED module with one bought from eBay (buyer says it is a new one and was tested). However, this replacement does same thing - the module keeps dimmed and one of LEDs is off (not the same LED). I used a multi-meter to obtain the source/input voltage from the white connector (to LED module): 29.5 VDC, My question is if the source voltage 29.5VDC is the issue or if LED module, and even control board is the root cause in this case?