Apparently it's very easy and possible to break the Secure Element NFC chip in android phones by flashing and factory resetting your device. This is the first article I found that says it can be fixed with a backup. Hopefully this helps prevent a headache for some users!
A Simple Factory Reset Could Break Your Google Wallet Forever, Learn How to Safeguard Your Info – Droid Life
A Simple Factory Reset Could Break Your Google Wallet Forever, Learn How to Safeguard Your Info – Droid Life