I have a problem with the power button of this phone and sometimes the voltage that reaches the button that is 4.19V drops to 2V, 1V or 0.63V and starts when the button fails, I start to get the message Shutdown, Restart, etc. It also no longer allows you to turn on the screen or the phone turns on when you place the battery.
But when it reaches 4.19V it works perfectly.
I have replaced the button since the one that the original one took off due to misuse and no longer worked, I also replaced the charging port and check that there was no short between pins.
Check the resistance of 100 Ohms and it's fine, as well as the capacitors that were not short.
What I suspect is the IC that may not work well.