What is causing the led voltage to drop on my tv?

the top half of my 50” led vizio tv is dimmer than the bottom half sometimes. I took apart the tv and found that 3 of the led strips were not working. When I turned on the tv for the first couple of seconds all of the leds work. However after a while the 3 leds i mentioned before turn off so that only half of the tv works. I measured the voltages and my LED1 pins showed that when i turn on the tv, it reads 100v but then suddenly drops to 0v. I think that it means it is a power board issue but i cant find anything on the board that looks damaged. Does anyone know what can cause the LED1 voltage to suddenly drop to 0v on the power board?

BOARD NUMBERS: FSP155-2PSZ01, 3BS0333913GP

MFR PART NUMBER: Vizio 0500-0605-0280