White circle, turns off while charging, from 0.5A to 0A, pics

Hello,

I have two S9 one with dead mainboard one with dead screen from ebay. On pictures from seller I could see that the phone was working.

After I switched the mainboard, the phone turns on to white circle with lightning icon

and turns off again. Both mainboards are SW-G960F_N V47.

My charger is from an ASUS tablet with 5.2V/1.35A.

I have three batteries with 3.7V (tried all of them, same result) and also the schematics. I have a multimeter and can measure the voltage and current drawn by the phone. Microscope and hot air station + soldering iron. I have no wireless charging.

https://imgur.com/a/amIp8pq

Thank you.

I applied power from a power supply to the battery connector (red) and put black probe to ground (shielding). Nothing happened. I did so because of this video: https://youtu.be/AXdFIYYintE?t=89

I assembled the phone to put it away and before doing so I connected it to a charger and it started working. I also reinstalled android and applied 2 updates.

Weird.