Infinite BootLoop (even when DFUing)

So here's what's happening.

I bought an iPhone 5C in the intent to repair it for a close relative. The phone was supposed to be completely dead, but i managed to bring back the apple logo somehow by doing nothing. I though that because the iPhone had no battery, I just had to buy one and everything would be fine. Guess I was wrong. The phone is still stucked inside of a boot loop. So her's what I tried. (also, the battery is genuine and has been tested with no problems inside an other iPhone 5c).

-DFU , not working (iTunes detects it, but the phone gets right back in a loop as soon as iTunes tells it to reboot).

-Restoration mode (same deal)

All the above, but without the rear camera, display, front camera, buttons or the antenna plugged in. I even tried another lightning assembly, camera, display, front camera).

-I double check that the screws were in the right place.

I also tried some 3rd party software like 3utools, imyphone, dr.fone (but to fix the phone, I apparently have to pay for the last two)

Nothing worked.

(also, in the bootloop, half the time (1/2 boots) the screen is fine and on the other boot, the screen is dim and has some slight green appearing in the top third).

The phone does this plugged in or not, but when plugged in, it's impossible to turn off.

Does anybody knows how to fix this phone with having to go inside a repair shop ? (I also have another iPhone 5c, but with no battery that I can salvage parts from).

(I included a video and two photos of the phone behavior)