migrated LVM2 VG to a different PV and now getting 'error: invalid volume' from update-grub

[Wladimir Mutel]

my Ubuntu is 18.04.2 with all updates applied
in the past my VG resided on /dev/md1 PV
I installed new HDDs, created /dev/md0 (this name was unused since previous PV migration some years ago), updated /etc/mdadm/mdadm.conf , moved LVs from /dev/md1 to /dev/md0 (with pvmove), removed /dev/md1 PV from the VG, then stopped and removed /dev/md1 , then updated mdadm.conf again.
I regenerated initrd image by dpkg-reconfigure to include updated mdadm.conf
and now, when I run update-grub , I get this :

Sourcing file `/etc/default/grub'
Generating grub configuration file ...
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
Found linux image: /boot/vmlinuz-4.15.0-46-generic
Found initrd image: /boot/initrd.img-4.15.0-46-generic
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.
error: invalid volume.

I am not sure what could be the cause of this behavior.
How can I tell what volume exactly is invalid and how can I fix this situation ?
The only potential problem I see is that now I have 2 FAT copies for EFI boot partition having identical UUIDs.