Yesterday I replaced my screen + digitizer with a non-OEM screen (don't do this! not worth it at all! use OEM with it's hard glass). The repair was easy and accident-less. Absolutely everything works now except for the camera and its flash, with errors "Can't connect to camera" and a crash of the flashlight app respectively.
After googling about it, I've tried these solutions: soft reboot, bootloader reset, deleting camera app data, re-updating camera app, safe mode boot, uninstalling flashlight app and Nova Launcher.
After none of these worked at all, I teared my phone apart again to clean the connections with some ISO alcohol and cotton swabs. Didn't work. The only thing I've haven't tried is factory reset.
I may try the factory reset and use the opportuninty to flash Android L if there's no other solution suggested here.
ps: phone is really easy to repair.
edit2: bug report:
screenshot of error (taken by bugreport)
edit: here are some pics I took of the camera