Hey, You’re a great discoverer. I had this blinking red LED thing for couple of weeks on my Z2. It shows battery is full & in a sudden goes down to 40-50% & sometimes to 0% which immediately turn off the device. I thought it was a battery or software issue. yesterday I restored my phone with factory defaults. But it didn’t help. Just found your comment here “Flashing red light could mean that your battery is not being detected.” AND “I figured out the problem when the phone went from empty to full each time I pressed top third of the back cover plate.” My fault is gone as I re-fixed the battery connection. It is over three years I’m using this mobile yet didn’t find an issue. THANK YOU VERY MUCH!