I have a Nexus 5 that a friend gave a while ago. The phone came directly from google in Mountain View meaning this is/was a prototype phone. (It has a SKU number and a 'NOT FOR SALE' legend in the back)
The really interesting thing about this phone is that in model number it was saying "Nexus 4" even if in fact it is a nexus 5.
The phone was working perfect except for the google play that was crashing every time when I tried to open it. I factory reset the phone several times with no success. The android version it was 4.2.2 (If I remember right)
I decide to flash the phone with a newer version. I flashed everything (system, recovery and radio) with hammerhead 4.4.3.
After this update, I'm not able to connect to the network. If I try to make a call, it display: "to place a call, first turn off airplane mode".
When I go to phone info and try to "Turn on radio" it doesn't do anything.
I reflash all available modem versions with no success.