RAID Detection using intel VROC (VMD)

Hello,

At the moment I‘m struggling with some newer Dell Precision workstations using „software raid“. The used kernel is Debians 5.10.0-8 which is capable to detect raid-volumes with vroc.
The hardware part:
2 hdd (Toshiba 2 TB)
2 SSD (PCI NVMe 512 GB SK Hynix)

Both sets are configured to use raid1.
Already installed using whole disk raid1 with pre-installed Windows 10 Pro, so I would like to preserve always partition 1,2 (efi (500MB), msftres (128MB)) and at the end one msftres for recovery (1100MB) so partition 3 should be resized to 380GB (instead of 450GB).

Booting fai detects only the ssd and hdd, but not the raid-volumes. At that stage setup-storage fails, because I specified md124 for disk_config-file.
When I run:
mdadm -A /dev/md/md0 -e imsm /dev/nvme0n1 /dev/nvme1n1
mdadm -A /dev/md/md1 -e imsm /dev/sda /dev/sdb 
mdadm -- manage /dev/md/md0 -- run
mdadm -- manage /dev/md/md1 -- run

the raid volumes are running on md126 and md127 and two new volumes are detected using dev names md124 and md125.
Deleting /var/run/fai/FAI_INSTALLATION_IN_PROGRESS
and calling 
/etc/init.d/rcS

Installs Debian just fine. Grub is installed using grub-efi (it seems without problems), but the created grub.cfg has two options (each of them for one detected Windows installation)
Rebooting to the just installed Debian works.
Calling „update-grub“ as root detects than only one Windows (on the raid volume) but „destroys“ the running grub.cfg
On next reboot grub can‘t find the configfile
And the grub prompt showed up:
grub>

Grub detected than two hdd:
hd1 and hd2 
Where hd2 is the nvme raid.
Calling 

set root=‘hd2,gpt5’
insmod gzio 
linux /boot/vmlinuz…. root=LABEL=ROOT ro quiet apparmor=0 ipv6.disable=0 net.ifnames=0
initrd /boot/initrd….
boot

Is able to boot the installed Linux.
But rerunning update-grub doesn’t help, so I tried to re-run grub-install without success.

So two problems: 
- how can I get fai to automatically detect the existing raid?
- how can I get grub-efi to find the grub.cfg after running update-grub later

Thanks for any hints

Sven Schumacher