I got this too on my bq E5 HD when I updated to OTA13.
After the update progress bar completed, the screen just turned off.
Since I read about the issue already, I decided not to do the same which is to do hard reboot or long press of the power button.
As I read here, I connected my phone to power then the screen turned on for a couple of seconds but it was blank and turned off again.
I pulled the plug then that's when my phone completely rebooted.
This issue seems to be encountered by many and I think this should have been captured by the testers.
I got this too on my bq E5 HD when I updated to OTA13.
After the update progress bar completed, the screen just turned off.
Since I read about the issue already, I decided not to do the same which is to do hard reboot or long press of the power button.
As I read here, I connected my phone to power then the screen turned on for a couple of seconds but it was blank and turned off again.
I pulled the plug then that's when my phone completely rebooted.
This issue seems to be encountered by many and I think this should have been captured by the testers.