820-01700 Shuts off shortly after login


Hi guys

I have this 16-inch which powers on and boots fine.

But after around 1 minute of use the fans blasts up to full for one second and then machine turns off.

It doesn't turn off at the login window. It also doesn't turn off in Target Disk mode. I tried booting from an external USB harddrive with known good system and the issue persists.

I cloned data from the machine to an external hard drive (as it isn't shutting down in Target Disk mode) and from this drive system works fine in another machine.

I tried DFU restore. Restores firmware fine but also turns off while installing the new macOS already at the Activation Lock dialog.

Board is spotless. No liquid, minimal dust. History is that it just happened one day.

Any hints on where to start?