Cannot upgrade or downgrad BMW MKiV unit

[Marcel RSD]

This is the first unit facing this problem.
I put in a downgrade CD, screen is telling that the software will be loaded, turns black and stays black. Not even the grey/blue update screen with the progress bar. After a few minutes the disk is ejected. Still all what I see is a black screen. I push OK to get the unit restarted, see some flickering and that's it.
After disconnecting the power and wait for > 1 min, I get the video screen (light blue, white letters) and no navigation option anymore. If I the take my CD with the modded firmware, it is being read, ejected. But that's it.
If I use the original CD which I have used with the firmware what was installed on this unit, it is being read. But after eject I have to disconnect the unit. Wat 1 minute and then it's all back. But of course with the original firmware and splash screen.

The CD's I am using do the work on all other units, except this unit. Can it be a worn laser what is causing all of this or is it in the unit itself ? Because I have no explanation why the update screen with the progress bar is not shown.

Thanks,