If your having problems getting flashing starting, you can try pressing powerbutton 30seconds while usb cable is connected and flasher has been started for hard reboot, usually that goes to flashing mode directly.

More drastic way is to remove the battery and connect the cable and start the flasher, and then reconnect the battery. Only 1 device out of 10000 needs dismantling in order to revocery.

And if bootloader is really blanc and device doesnt respond even to hard reboot, then you can use "-c" flag for cold reflash.