The strange thing is that the keyboard is lit and the notebook appears to be still running. I suspect that it goes into a kind of sleep mode, because after the reset the values are read from NVRAM and switch to this mode. Only when the BIOS is reset, and with it NVRAM, will MacOS start normally.
What else can you do with the flashing display when starting up? When the computer starts and the apple logo can be seen, it flashes several times and there are strange stripes (artifacts), shortly before the login occurs, the login appears and the display switches off for 2-4 seconds (also the lighting keyboard) and then it comes back. Could it be that the wrong device ID is being used, or that other parameters need to be changed?