Boot loop and only starting with charger

The phone does not respond at all without an external power supply. When connecting to the pc, it goes in a boot loop, where it stays very short at the samsung logo, then reboots… when connecting to a fast charger, it’s the same but its staying about 2-3 seconds longer at the samsung logo….

I did reflash the firmware with odin wich worked also not in a normal way… i had first to repartion the device whithout to flash anything, then reboot (doing both in one step did not work) and then i was able to flash the firmware (after i tried a lot of things first because flashing was not possible). So at least it seems so as if the nand is not dead?

But what is it..? If the power ic was dead, it would not even work with the charger?… Is it the battery?

*I am able to go to download mode, where it stays stable with charger*

Showcase: https://youtu.be/O718OwZIoHc