EDIT: The device seems to no longer boot into CM12.1 SFOS at all, I left it for about 8 hours and the only thing that happened was the LED came on. Out of sheer curiosity, I flashed CM13 SFOS over the CM12.1 base and it surprisingly showed more signs of life than the CM12.1 SFOS, in the form of vibrations and the LEDs going on and then dim like on the Ahoy screen and the red shutdown LED.