I have installed a RAID1 system up to the point that GRUB errors out.
Then I executed a shell, chrooted to the target system and updated the packages (including grub).
After the updates were installed, I exited back to the installer, installed the Grub bootloader using the menu item and it worked like a charm, no error message at all.
(I started the installation from an Alternative disc in Expert mode.)
I can confirm that the updates work.
I have installed a RAID1 system up to the point that GRUB errors out.
Then I executed a shell, chrooted to the target system and updated the packages (including grub).
After the updates were installed, I exited back to the installer, installed the Grub bootloader using the menu item and it worked like a charm, no error message at all.
(I started the installation from an Alternative disc in Expert mode.)