unit won't charge while is on - brainstorming

[fra1110]

Hi, a client brought me this dude, t300 chi and i noticed that it won't charge until it's completely off.

I fully exclude windows 10 problem, because even in bios fw update utility, it asks for "plug in power adapter" so it doesn't work at all.

core M and 4 gig of ddr3 1500mhz ram 128gb ssd, never open.

things i've done:
- try another 19v power adapter 96w are quite enought - nothing's changed
- isoprophyl alcool on the adapter jack and nothing changed

this brought me to these options:
- INTEL MANAGEMENT ENGINE - I have to try to install last ME update
- BIOS update is not possible, there's v207 installed and v209 available, but i can't flash if there's no power adapter recognized -.-'
- HW FAILURE - the voltage regulator, or one of his arem, of the laptop is faulty (at last...)

now I have to try a workaround to flash bios without power adapter.

I'm so disgusted from asus and lack of utils... lenovo has a windows utils that allow to flash bios during windows time...

I update you folks if i found a solutions.

update:
i found that when battery is 100% flash bios utils is available.
so i updated 207 -> 209 but still same issue.
i updated management engine and other intel stuff.

none of the above get results.
but...

if i set battery on average mode from windows, it charge without problem during the daily use.
instead if I set performance mode, doesn't charge at all.