This is not bug but default option of update-grub. It is not normal to make use of one grub with two different update-grub from different roots. Instead you should edit /etc/kernel-img.conf to disable post[install/remove] update-grub,
This is not bug but default option of update-grub. It is not normal to make use of one grub with two different update-grub from different roots. Instead you should edit /etc/kernel- img.conf to disable post[install/ remove] update-grub,