Had this happen on one of our 920's and it appeared to be the CNN app. We had 2 920's side by side and verified that each setting on the phone was exactly the same then uninstalled apps one by one until it went back to normal and once the cnn app was removed the battery went back to normal consumption levels.
Might be a coincidence or a corrupt installation but if you have it installed try removing it.
I herd the volume up and power button, this sent my phone to the flash setting. After that I held the power and volume button down and the phone than loaded normally, without ever actually flashing the software.