iPhone motherboard current fluctuation
Hello! I got an iPhone 12 that does not turn on. No visible damages, no breaks, no water damage. Took it apart, connected to a dc psu, no current draw without booting. With trying to boot, it starts to draw a weird amount. It fluctuates between .400 and 0, with like 2 different spikes starting from each end, getting close to the other end, then back, and the cycle continues. Here's a vid about it:
https://youtu.be/BXc8cXyvBLs
It doesn't get hot (at least not on the upper side of the board), my sandwich heater didn't arrive it yet, and I dont want to take it apart unless it's necessary. Any ideas what could be wrong here?
Any help is appreciated!
Have a nice day!