Well when I look at the advanced radio settings I keep getting "imei: unknown" status at my nexus 4. Together with baseband unkown and all mobile connectivity seems wrong. I am currently running the stock run and not updated anything or done anything (heck I took great effort to "relock" it when I unlocked it to FIX this. (On top of this: loading takes ages, sometimes refusing to load till battery level drops below 10%).
I've tried flashing android 4.4 (but this creates the soft-brick looping while starting android).
I've tried factory reset,
I've tried hard reset
And I've tried the manual resets by flashing 4.2.2 back on.
In all combinations
What can be done, and how can I start using my mobile phone as a PHONE again? Anything but asking for a warranty (as I sadly void It when I had to downgrade from 4.3 to 4.2 to fix a bug introduced in 4.3 that prevented deep sleep)