Took my old iPhone 5 (now belongs to my wife) to Apple store under AppleCare plus warranty for battery issue. It would show 20% charge remaining and then shut down. After testing the battery was bad. There is also a hair line crack on the front that they said is very rare but is manufacturing not from a drop. Wasn't dropped and also no nick in glass. They offered a replacement on the spot but I asked if battery could be replaced. The iPhone is signed on the back by Atlanta Falcons Quarterback Matt Ryan. They were very accommodating and said they would put in a new battery and even replace the front (screen and glass). Said see you in an hour. 2 hours later with iPhone in hand they explained they couldn't get it out of DFU mode. They did and gave it to me to sign in to restore from iCloud. It my wives so I didn't have her login and password so asked if I could do later and she said yes and if there was an issue with it looping back into DFU to bring it back to swap for a new one. Took it home to have my wife restore and it would not respond to pushing power or home buttons. I plugged it in and the screen then came on and the iPhone responded. My wife put her info in and it started it's restore. It got to the end and went into DFU showing plug into iTunes. I plug it into iTunes and it show the iPhone but says no serial number. I went through the restore and update. It failed time and time again. Buttons wouldn't respond and I would have to plug it in every time to get it to wake up and try and restore. It would just go into DFU every time. Weird ... Will have it swapped for another which is a 2 hours round trip for me. Anyone heard of an iPhone having the serial wiped after service? Did they replace such a pivotal part that the iPhone lost it's core programming? Sorry this is a book but wanted to share the full story.