PS5 boots right into loading bar "processing" and stuck at 99%

My PS5 Disk Version shows a progress bar right after start. Its seems to be stuck at 99%. I even left it for around 12h but nothing happened.
My idea was to reinstall the system software via safe mode, but also there it only shows the progress bar and not let me use the safe mode menu.
I also tried to remove the disk drive, but same behaviour.
Since there is not a single similar issue mentioned on the internet, maybe someone here has an advise for me?

Issue Screenshot:
https://imgur.com/lCuxZxi

thanks in advance,
Rob