iPhone 6 in boot loop after screen replacement
So i have replaced a Iphone 6 Display (pre-assembled) and everything worked well (tested fron camera, homebutton and stuff).
Suddenly my friend told me, that somehow the device is not working and when he gave it to me (the same day) the iphone was stuck in a boot loop:
I tried to disconnect battery and also the reset with home button and power button, but still the same problem. Funny thing is, that I cant put it into DFU (it seems), because the device is restarting too fast. After that I tried to take another Display (from my working device) but the problem is the same.
I did not use the wrong screws (3 smallest bottom, biggest on the right, middle left)!
Please ifixit and community help me out :(
Thanks in advance.