Nexus 5 screen only showing vertical lines

I dropped my Nexus 5, the display broke and was only showing vertical lines in all colors.

So i bought a new display+digitizer and followed a guide to replace the old one. Everything worked well, i started the device and saw the Google logo. Perfect!

Then I wanted to charge the device, and as soon as i plugged the power adapter the fancy vertical lines where back on the screen.

Thinking the usb port might be broken i bought a new daughterboard and installed it. No changes.

Does anyone have an idea whats my problem here? Why did it work for a few seconds after installing the new display?

Thtanks a lot!