Yes, this is a bug and I think I know how to fix it. Sorry, it is hard to spot such bugs without having N810. Meanwhile as a workaround you can force the menu to appear everytime by running Code: chroot /mnt/initfs cal-tool --set-root-device ask:mmc2 as root on your tablet. The 'ask' part is important, mmc2 is preselected choice.
chroot /mnt/initfs cal-tool --set-root-device ask:mmc2