820-4924-A strange power button issue

[KC Micro Tronix]

The power button works. If you press it you turn on the machine. If you hold it you turn off the machine.
>> if you quick press it << you freeze the machine and lock it up.

My guess is I have a CPU FET problem but I don't have much experience with these older machines.

 

[2informaticos]

Do you need a very short press time?
Can that be done accidentally by the client?
SMC reset restart it from that stage?

 

[KC Micro Tronix]

quick tap at any point freezes it.
I can power cycle the machine by holding and duplicate at will

I can remove power and power on with mag safe. And when it boots up if I quick tap the power button it's frozen
If I don't touch it that machine runs fine.

 

[2informaticos]

Tried PRAM reset?

SMC_ONOFF_L recovers instantly after such short press, or has some delay on low level?
Same thing happens if acting rapidly over R5116 pads, instead of power button?