I recently got a replacement nexus after my first one refused to turn on. Shop exchanged it immediately in store. New phone has been fine. Subjectively even a little faster maybe. I put in the extended battery today and when it rebooted it went into odin mode with a message saying downloading do not turn off target. I waited a while then just pressed the off button anyway and the phone rebooted fine. Searching forums this odin mode and following mesage seems to be a feature of a rooted phone. Could it be my phone is not brand new and has been previously rooted. If so seems like a good reason to get another replacement no?