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How much time between restarts?

PPBUS_AON stable 12.3V? What is diode mode to ground at 3V8_AON?

Keyboard can't work without good trackpad. You should test with known good (compatible) trackpad board/flex.

Applying voltage without any previous checkings? Do you have same 0.012 reading on any coil from secondary power supplies derived from PPBUS_AON?

It should have a separation fuse for PPBUS_AON. "The voltage at the PPBUS_AON diode is 0.012V" I'm not sure what this means. I always said NEVER write end "V" for diode mode readings; just to avoid a confusion between voltage and diode readings. If you really have 0.012 in diode mode, that is...

Guided by A2681 (02536), disconnect F5200 and check C5252 voltage.

Check big coils voltage with board alone on the desk; nothing connected, apart of charger.

Which schematic are you using? "PPBUS_AON line has an abnormal value of 0.075V" If that is voltage, what is diode mode to ground reading? Remove battery + charger and wait 15s before checking.

Is the machine recognized in DFU?

Do you get voltage on any coil before restarts? Also check U7800 LDOs, G3S and SSD voltages.

Many coils you didn't check there. Anyway as RAM voltage is missing, the board doesn't boot. Any fault history available? It is recognized in DFU?

Be sure to use 96/140W charger. Also test with charged battery.

Stuck on apple logo, or goes black/off?

Possibly more liquid damage on secondary power rails, or other sensors. What about M/SPMU LDOs? Compare diode mode readings with good board. Did you test with charged battery?

Both R8450/1 have correct ohm value? Check U8450 output voltage also.

"IPD_SYS_AWAKE is present *without* trackpad connected" In such case, CPU is the one which first wakes up the trackpad. Seems that even you force on the trackpad, CPU doesn't talk with it. I suppose that CPU can't start such communication, without sending AWAKE signal by itself.

So board reacted at heat applied on the NANDs replacement process. I still suspect some leakage caused by corrosion somewhere.

"I ran a wire from pin 1 to pin 3" Pin 4 went high then? Check IPD_LID_OPEN_1V8 and IPD_WAKE_CONN_L; compare with good board. BTW, check JT400 signals when trackpad is connected. I hope its power rails are all good.

Then something else is affected by corrosion. Can be just one resistor, or capacitor; not easy to find. BGA chips are suspect also.

Did you test with known good (2015 year) screen?