Confirming the bug. This is caused by udev trying to assemble the md device with --incremental. The /var/run/mdadm directory is missing from the initramfs image and the array map is not created and mdadm gets confused.
The solution is to add the following line to /usr/share/initramfs-tools/hooks/mdadm
mkdir -p ${DESTDIR}/var/run/mdadm
After this, the array is assembled correctly on boot
Confirming the bug. This is caused by udev trying to assemble the md device with --incremental. The /var/run/mdadm directory is missing from the initramfs image and the array map is not created and mdadm gets confused.
The solution is to add the following line to /usr/share/ initramfs- tools/hooks/ mdadm
mkdir -p ${DESTDIR} /var/run/ mdadm
After this, the array is assembled correctly on boot