Lenovo Ideapad 15IIL05, turns on and off with charger BUT works by injecting 20v after main mosfets

[NanoTesting]

I got a 15-IIL05 that failed to turn on BUT IT DID TRY TO TURN ON and then turned off after 30+- seconds, i disassembled it and found a screw loose inside the case.
With charger it turns on, fan spins but gives no image.
Tested main mosfets no short, tested 3.3v,5v,DRAM, CPU etc and they were present.
Reflashed BIOS, same problem.
Replaced both main mosfets.
Checked main mosfets again and i noticed that they closed once the laptop shut down, so i decided to bypass them and used a bench PSU to check how much power the laptop was drawing while trying to turn on, 20v@3A, and it drew around 12w... and the laptop turned on and booted into windows.
What could i check to see what is causing them to close and not let the PC start? nothing seems to be overheating but i don't have a thermal camera to check properly
Around BQ chip i guess but exactly what should i be looking for?

Attaching schematic and boardview. MOD EDIT: Please post a link to the schematic/boardview

[pc_okay]

Hello,

You may try With battery alone first and with another charger.
Then Check your first mofsets resistance (source>> Gate , G >>S, S>>D…)(without power!)
You may Check résistances around your shunt résistor too.(without power)
Check prochot voltage on your BQ, never know…(With system power on With charger)

good luck !