Nexus 5 front camera not working
I found a solution:
If you don't have a RMA option like me, it's possible it can be fixed with just disconnecting and reconnecting the front facing camera.

Try deleting cash, reinstalling camera, safe mode, factory reset, etc. before doing this.
Proceed at your own risk!

As shown in this video: https://www.youtube.com/watch?v=OPuCmfhzgbg)


Remove the back of the phone (beginning of the video).
Unscrew the top plastic plate (7:15 - 8:10).
Disconnect and reconnect front-facing camera flex cable (13:43 - 13:57).
Put everything back together and you're done.


Viola!
I hope it helps someone.

UPDATE: It stopped working again and this didn't help anymore. I had to buy a spare part and according to the video above replace it. The repair was succesful though.